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1.
The activities and substrate specificities of extracellular enzymes in natural systems are not well understood, despite their critical role in microbial remineralization of organic carbon. These enzymes initiate organic carbon degradation by selectively hydrolyzing high molecular weight substrates to lower molecular weight products which can be transported into cells. A set of single- and dual-labeled fluorescent polysaccharides was synthesized and characterized to explore a variety of approaches for measuring enzymatic hydrolysis of biopolymers via photophysical techniques, focusing particularly on rapid and robust optical techniques which are amenable to field measurements in remote locales. A shotgun-labeling approach yielded dual-labeled probes that exhibited substantial donor fluorophore quenching. The photophysical response of these probes to hydrolysis via purified enzymes was investigated in the lab, and fluorescence polarization proved to be a rapid and reliable technique for monitoring probe hydrolysis. Initial field results were also obtained from hydrolysis experiments in sediment porewaters. Because polarization measurements are rapid and simple, this approach could be used to follow the extracellular enzymatic hydrolysis of a wide range of biopolymers which fuel microbial metabolism. 相似文献
2.
为研究带鱼(Trichiuruslepturus)蛋白复合酶解液中抗菌肽(ABP)的抑菌性及表征活性,本文以舟山小带鱼为研究对象,制备蛋白抗菌肽。研究得到抗菌肽分子量在区间(3000Da, 3000—800Da,800Da)内均有分布,在3000—800Da区间内含量达到49.61%,酶解程度最深,氨基酸总量为881.83mg/g,必需氨基酸与氨基酸总量比为44.75%,必需氨基酸与非必需氨基酸比为81.33%,营养价值高。六类提升抗菌效力的氨基酸占氨基酸总量42.71%,抗菌效力较高,具有广谱抗菌活性,为阳离子型抗菌肽,对G–具有较强的抑菌效能。抗菌效力与稀释128倍(10.15U/mL)土霉素抗菌效力相当,与稀释4倍的硫酸链霉素(325U/mL)抗菌效力相当。对抗菌肽的表征活性进行研究表明:该抗菌肽在pH 2—12下溶解度良好,均大于88%,有强适应性;乳化性随pH增大而增强, pH 4时乳化性最低,为53.68%,在pH 12时达到最高值78.34%;乳化稳定性在pH 6时达到最高,为85.83%, pH环境过酸或者过碱的情况下乳化稳定性均较低;发泡性随pH上升呈现增长趋势,在pH 12时达到最大值57.33%, pH 4时抗菌肽泡沫稳定性最低,为22.86%, pH升高,泡沫稳定性也随之增强,在pH 12时达到最大值59.58%。该研究结果对探究带鱼抗菌肽的各项性质提供了理论依据,对带鱼抗菌肽的应用研究具有一定的理论指导意义。 相似文献
3.
Advances in analytical techniques now allow for the potential analysis of intact peptides and proteins isolated from marine sediments. However, there is no established technique for the extraction of macromolecular materials from marine sediments. Six different methods for extracting the amino acid component from coastal marine sediments were compared to the standard hot acid hydrolysis technique for their percent recovery and amino acid composition. The standard hot acid hydrolysis on dried, whole sediments released the greatest concentration of total amino acids (PS-THAA; 3.52 mg gdwt− 1 ± 10% (SMD)), yet this only accounted for 22% of the total nitrogen in Puget Sound sediments (Washington, USA). Repeated hydrolysis of the same samples did not improve the recovery of nitrogen by more than an additional 10%. Base extraction (0.5 N NaOH) was the second best method for recovering amino acid nitrogen, releasing 60% of the Puget Sound total hydrolyzable amino acids (PS-THAA) (corresponding to 13% of the total sedimentary nitrogen), and has the advantage that it does not rely on peptide hydrolysis to free the nitrogenous component from the sediment matrix. The amino acid distribution of the 0.5 N NaOH extract was not significantly different than the initial THAA. Other non-hydrolyzing methods released lower yields of amino acids (Triton X-100 ≥ hot water > 50 mM NH4HCO3 > HF), but might prove to be of use to investigators interested in specific fractions of sedimentary organic nitrogen because these four methods had distinctly different amino acid compositions (enrichments in basic amino acids and depletions in acidic amino acids). Treatments with HF both before and after traditional hydrolysis and/or extractions with base did not release any more of the sedimentary nitrogen. Our results are consistent with the hypothesis that a large fraction of the sedimentary nitrogen (TN) is protected within an organic matrix. 相似文献
4.
The observation that a fraction of organic matter produced in marine systems evades the concerted efforts of microbial communities and is buried in sediments suggests that there are ‘speed bumps’ in carbon degradation pathways that impede microbially driven remineralization processes. The initial step in degradation of macromolecules, extracellular enzymatic hydrolysis, is often stated to be ‘the’ rate-limiting step in carbon remineralization. Experimental investigations described here, however, demonstrate that at least in certain cases, microbes produce extracellular enzymes on time scales of hours to tens of hours in response to substrate addition, and hydrolysis is extremely rapid. If enzymatic hydrolysis can be rapid, what factors slow or stop organic matter degradation? A lack of the correct inducer to initiate enzyme production, and/or a lack of the correct organism to produce the required enzyme, may result in a complete lack of hydrolysis in certain environments—a barricade, rather than a speed bump. Preliminary evidence supporting this hypothesis includes a comparison of polysaccharide hydrolysis in seawater and sediments, which demonstrates that the spectrum of enzymes active in seawater and sediments are fundamentally different. Furthermore, a survey of enzyme activities in surface waters from a range of locations suggests that pelagic microbial communities also differ widely in their abilities to express specific extracellular enzymes. Trans-membrane transport through porins is yet another potential location of structure-related selectivity.Our efforts to identify speed bumps and barricades are hampered by our inability to structurally characterize in sufficient detail the macromolecular structures present in marine systems. Furthermore, assessments of organic matter ‘quality’ from a chemical perspective do not necessarily accurately reflect the availability of organic carbon to microbial communities. For these communities, in fact, ‘quality’ may be a variable, which depends on the enzymatic and uptake capabilities of community members. To begin to assess substrate structure and quality from a microbial perspective, we will have to combine specific knowledge of macromolecular structures with detailed investigations of the enzymatic and transport capabilities of heterotrophic marine microbes. 相似文献
5.
Sugars and uronic acids have been extracted from marine sediment and seawater by various hydrolysis techniques and analyzed by ion-exchange chromatography. All stages of the extraction methods were examined for sources of error arising from contamination, destruction and incomplete extraction. Tested were: (1) sample drying procedure; (2) acid hydrolysis, i.e., effect of different acids, variations in acid concentration and hydrolysis time, and effect of variations in organic and CaCO3 contents of sediment on the quantity of released sugars and uronic acids; (3) deionization, i.e., neutralization of acid by precipitation or by ion-exchange resins, separation of sugars from uronic acids; and (4) volume reduction, i.e., rotary evaporation, freeze-drying, effect of added glycerin. It is shown that the hydrolysis efficiencies of the acids tested varied with the nature of the organic matter in sediment. Simultaneous hydrolyses with different acids may give insights into the sources of the organic input and the environment of deposition. For all sediment types examined pretreatment with 72 w/w% H2SO4 gave the highest yields and is, thus the optimal hydrolysis method for sediment.Sugar and uronic acid yields from seawater varied with the type of acid used for hydrolysis. The highest yield for North Sea surface water was obtained with p-toluene sulfonic acid.Since most previous investigators employed non-optimal techniques, it is recommended that intercalibration studies be performed. 相似文献
6.
青鳞鱼下脚料水解蛋白的制取及其营养评价 总被引：11，自引：0，他引：11
以青鳞鱼（Harengula zunast)下脚料为原料，采用碱萃取，蛋白酶水解，浓缩，喷雾干燥等手段，制得水解鱼蛋白。研究了碱萃取，蛋白酶水解条件及不同沉淀方法对水解鱼蛋白沉淀效果的影响，并对水解鱼蛋白制品营养价值进行了评价，结果表明，下脚料水解鱼蛋白制品含粗蛋白72．9％，氨基酸总量67．6％，其中必需氨基酸占44．6％，氨基酸分为96，苏氨酸为其限制性氨基酸（1973年FAO／WHO标准），无机盐钙，镁，铁，锌，铜，磷含量丰富，以有机溶剂（异丙醇，乙醇)为沉淀剂沉淀水解蛋白时，粗蛋白损失率约为30％（干基计）。 相似文献
7.
《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(16):1055-1062
We found similar microbial degradation rates of labile dissolved organic matter in oxic and suboxic waters off northern Chile. Rates of peptide hydrolysis and amino acid uptake in unconcentrated water samples were not low in the water column where oxygen concentration was depleted. Hydrolysis rates ranged from 65 to 160 nmol peptide L−1 h−1 in the top 20 m, 8–28 nmol peptide L−1 h−1 between 100 and 300 m (O2-depleted zone), and 14–19 nmol peptide L−1 h−1 between 600 and 800 m. Dissolved free amino acid uptake rates were 9–26, 3–17, and 6 nmol L−1 h−1 at similar depth intervals. Since these findings are consistent with a model of comparable potential activity of microbes in degrading labile substrates of planktonic origin, we suggest, as do other authors, that differences in decomposition rates with high and low oxygen concentrations may be a matter of substrate lability. The comparison between hydrolysis and uptake rates indicates that microbial peptide hydrolysis occurs at similar or faster rates than amino acid uptake in the water column, and that the hydrolysis of peptides is not a rate-limiting step for the complete remineralization of labile macromolecules. Low O2 waters process about 10 tons of peptide carbon per h, double the amount processed in surface-oxygenated water. In the oxygen minimum zone, we suggest that the C balance may be affected by the low lability of the dissolved organic matter when this is upwelled to the surface. An important fraction of dissolved organic matter is processed in the oxygen minimum layer, a prominent feature of the coastal ocean in the highly productive Humboldt Current System. 相似文献
8.
The activities of extracellular enzymes that initiate the microbial remineralization of high molecular weight organic matter were investigated in the water column and sandy surface sediments at two sites in the northeastern Gulf of Mexico. Six fluorescently labeled polysaccharides were hydrolyzed rapidly in the water column as well as in permeable sediments. This result contrasts with previous studies carried out in environments dominated by fine-grained muds, in which the spectrum of enzymes active in the water column is quite limited compared to that of the underlying sediments. Extracts of Spirulina, Isochrysis, and Thalassiosira were also used to measure hydrolysis rates in water from one of the sites. Rates of hydrolysis of the three plankton extracts were comparable to those of the purified polysaccharides. The broad spectrum and rapid rates of hydrolysis observed in the water column at both sites in the northeastern Gulf of Mexico may be due to the permeable nature of the sediments. Fluid flux through the sediments is sufficiently high that the entire 1.5 m deep water column could filter though the sediments on timescales of a few days to two weeks. Movement of water through sediments may also transport dissolved enzymes from the sediment into the water column, enhancing the spectrum as well as the rate of water column enzymatic activities. Such interaction between the sediments and water column would permit water column microbial communities to access high molecular weight substrates that might otherwise remain unavailable as substrates. 相似文献
9.
The extent to which marine organic matter is associated with surfaces and the consequences of such associations for organic matter remineralization are the focus of considerable attention. Since extracellular enzymes operating outside microbial cells are required to hydrolyze organic macromolecules to sizes sufficiently small for substrate uptake, the effects of surface interactions–on enzymes as well as on substrates–for hydrolytic activity also require investigation. We used a simplified laboratory system consisting of a free (dissolved) polysaccharide (pullulan) and the same polysaccharide tethered to agarose beads to restrict mobility, plus the corresponding free enzyme (pullulanase) and the same enzyme sorbed to montmorillonite (Mte), to investigate systematically the consequences of surface associations of enzymes and of substrates on hydrolytic activity. Changes in substrate molecular weight were monitored with time to measure the course of enzymatic hydrolysis. Although hydrolysis of free substrate was nearly complete after 2 min incubation with the free enzymes, the sorbed enzymes also effectively hydrolyzed free substrate, and the data suggest that they retained activity longer in solution compared to the free enzymes. Sorbed enzymes progressively hydrolyzed the free substrate from > 50 kD to lower molecular weights during a 24 h incubation, with a final product distribution on average showing only 1.4% and 10.3% of substrate still in the > 50 kD and 10 kD size classes, while 46.6%, 29.3%, and 12.5% of substrate was in the 4 kD, monomer, and free tag size classes, respectively. This product distribution was very similar to that of the free substrate/free enzyme experiment. Tethering the substrate to agarose beads led to lower substrate release (2–3% of total substrate after 98 h incubation) into solution compared to the free substrate case. For tethered substrates, the state of the enzyme (free or sorbed) measurably affected the molecular weight distribution of the hydrolysis products, with free enzymes producing a higher fraction of high molecular weight hydrolysis products (28.7 ± 5.4% of substrate > 50 kD at the end of the incubation) compared to sorbed enzymes (11.6 ± 2.8% of substrate > 50 kD at the end of the incubation.) Tethered substrates were also hydrolyzed in a sediment slurry from surface sediments from Cape Lookout Bight, North Carolina; 0.1% of total substrate was released by enzymes naturally present in 1 cm3 of sediment after 144 h incubation, demonstrating that the enzymes naturally present in marine sediments are also capable of accessing tethered substrates. These investigations suggest that surface associations of enzymes in marine systems may extend the active lifetime of such enzymes, providing an opportunity for hydrolysis over longer periods of time and producing a different size spectrum of hydrolysis products relative to free enzymes. Furthermore, in well-mixed systems, surface-associated enzymes can hydrolyze substrates whose mobility is restricted, highlighting the importance of processes such as resuspension and bioturbation on organic matter remineralization. 相似文献
10.
采用生物蛋白酶酶解罗非鱼鱼排蛋白,以水解度(DH)为指标,进行了单酶、复合酶酶解效果的比较分析,并利用响应面分析方法(RSM)对酶解参数进行优化。结果表明,采用风味蛋白酶和木瓜蛋白酶双酶组合分段酶解,固定总酶添加量为3.0%、双酶复合比2:1、酶解时间3h、分段酶解时间比0.6:1,酶解温度56℃,分段酶解pH为7.0和6.2时,酶解效果最佳,罗非鱼鱼排蛋白水解度达到32.49%,酶解产物中游离氨基酸含量达32.84mg/g鱼排,占罗非鱼鱼排总氨基酸含量的25.43%,其中呈味氨基酸含量达18.48%,必需氨基酸含量达67.96%。 相似文献
11.
A survey of a Ligurian tourist harbour was carried out during winter 2006 and summer 2007 in order to study the organic matter (OM) turnover through extracellular enzymatic activity. Seawater and sediments were sampled at six stations, three inside the port boundaries, one outside the port and two in an area influenced by the outflow of a minor river (Boate). The seawater showed OM turnover times similar to other oligo-mesotrophic coastal areas, and low concentrations of chlorophyll-a and inorganic nutrients. The sediments, instead, revealed high OM loads and a predominance of proteolysis. A significant reduction of the OM loads was observed in the outside station, indicating that the OM accumulation was due to the structures and activities of the harbour and to the Boate influence. The OM biotic recycling via enzymatic activity was enhanced especially during summer. Although the carbohydrates were probably highly refractory, their turnover was notably faster, due to glycolytic enzymatic activity that was enhanced more than the proteolytic in both the sediment and in the seawater. This suggested that the removal and recycling of OM were potentially efficient, and prevented the shift to eutrophication of the Rapallo harbour area. 相似文献
12.
David J. Carlson Lawrence M. Mayer Mary Louise Brann Timothy H. Mague 《Marine Chemistry》1985,16(2):141-153
Several monomeric organic compounds, including amino acids, sugars, and fatty acids, were found to bind abiologically to dissolved macromolecular materials in particle-free seawater at natural substrate concentrations. The binding primarily occurred in ocean surface waters, at rates slower than in situ biological utilization rates of most of the compounds. Seasonal patterns of binding in Gulf of Maine waters may have been related to seasonal variations in macroalgal exudation of polyphenolic materials. Enhanced reactivity of relatively hydrophobic monomers implicated hydrophobic effects as potentially important in marine organic condensations. The resultant condensates showed high particle reactivity, consistent with low concentrations of dissolved condensed materials in seawater. 相似文献
13.
Raoul A. Daumas 《Marine Chemistry》1976,4(3):225-242
The relationships existing between the protein-containing fraction of particulate matter and amino acids dissolved in seawater were studied in the Gulf of Marseille at different periods of the year. The concentration of particulate proteins was almost zero in February and attained maximum values during April and May, the average concentrations of dissolved amino acids (total) varied between 900 and 1200 nmole l?1 but larger variations were encountered at the surface and in the vicinity of the sediment. The influence of meteorological conditions and the effect of the sediment on the distribution of nitrogenous substances were taken into account. Combined dissolved amino acids were more abundant than free dissolved amino acids in 90% of the cases. The concentrations of dissolved amino acids observed in a zone bordering the North Mediterranean are comparable to those found in other regions of the world. 相似文献
14.
The active lifetime of extracellular enzymes is a critical determinant of the effectiveness of enzyme production as a means for heterotrophic marine microbes to obtain organic substrates. Here, we report lifetimes of three classes of extracellular enzyme in Arctic seawater. We also investigated the relative importance of photochemical processes and particle-associated processes in inactivating extracellular enzymes. Enzyme inactivation in filtered seawater was slow, with apparent half-lives of enzyme activities on the order of hundreds of hours. The presence of particles (including cells) did not significantly change inactivation rates, suggesting that the long half-lives observed in filtered seawater were realistic for enzymes in unfiltered seawater. Phosphatase and leucine aminopeptidase were susceptible to photoinactivation, but only under high intensity UV-B and UV-C illumination; there was no evidence for increased inactivation rates under natural illumination at our study site in Ny Ålesund, Svalbard. Comparison of inactivation rates of commercially-obtained enzymes from non-marine sources with the extracellular enzymes naturally present in Arctic seawater suggests that the natural enzymes contain structural features that confer longer lifetimes, consistent with observations reported by others from a range of field sites that cell-free enzymes can contribute a substantial fraction of total hydrolytic activity in the water column. 相似文献
15.
Extracellular enzyme activities were compared among surface water, bottom water, and sediments of the Delaware Estuary using six fluorescently labeled, structurally distinct polysaccharides to determine the effects of suspended sediment transport on water column hydrolytic activities. Potential hydrolysis rates in surface waters were also measured for the nearby shelf. Samples were taken in December 2006, 6 months after a major flood event in the Delaware Basin that was followed by high freshwater run-off throughout the fall of 2006. All substrates were hydrolyzed in sediments and in the water column, including two (pullulan and fucoidan) that previously were not hydrolyzed in surface waters of the Delaware estuary. At the time of sampling, total particulate matter (TPM) in surface waters at the lower bay, bay mouth, and shelf ranged between 31 mg l−1 and 48 mg l−1 and were 2 to 20 times higher than previously reported. The presence of easily resuspended sediments at the lower bay and bay mouth indicated enhanced suspended sediment transport in the estuary prior to our sampling. Bottom water hydrolysis rates at the two sites affected by sediment resuspension were generally higher than those in surface waters from the same site. Most notably, fucoidan and pullulan hydrolysis rates in bay mouth bottom waters were 22.6 and 6.2 nM monomer h−1, respectively, and thus three and five times higher than surface water rates. Our data suggest that enhanced mixing processes between the sediment and the overlying water broadened the spectrum of water column hydrolases activity, improving the efficiency of enzymatic degradation of high molecular weight organic matter in the water with consequences for organic matter cycling in the Delaware estuary. 相似文献
16.
从微泡菌属AG1（Microbulbifer sp. AG1）克隆得到1302 bp大小的琼胶酶基因，该基因编码产物为一个成熟蛋白（413个氨基酸残基）外加一个信号肽（20个残基）。将不含信号肽片段的琼胶酶在E. coli BL21 （DE3）中进行了异源表达和纯化。使用琼脂糖作为底物，该重组琼胶酶的最适反应温度和pH分别为60℃和7.5。该重组酶表现出优良的热稳定性，在50℃和60℃下处理1 h，重组琼胶酶仍能分别保持67%和19%的残余酶活力。除了SDS，重组琼胶酶对于其他测试的抑制剂、去垢剂和尿素变性剂有着较好的抗性。利用薄层色谱和以对硝基苯-α/β-D-吡喃半乳糖苷为底物的酶活力分析结果表明，该重组琼胶酶为β型琼胶酶，它水解琼脂糖的主要终产物为新琼四糖，而且不同聚合度的酶解产物具有抗氧化活性。 相似文献
17.
《Marine Chemistry》2001,73(3-4):319-332
The accumulation of dissolved organic matter (DOM) at the air–sea interface is controlled by dynamic physical processes at the boundary between ocean and atmosphere. Much of the DOM concentrated in the surface microlayer is thought to be protein or glycoprotein. Enzymatic hydrolysis of these and other biopolymers is an important step in the microbial uptake of dissolved and particulate organic matter in many aquatic environments. We employed a sensitive fluorescence technique to investigate differences between extracellular enzymatic peptide hydrolysis in the sea surface microlayer and corresponding subsurface water from Stony Brook Harbor, NY. We separated the microlayer from its underlying water and thus measured hydrolysis potential rather than an in-situ process. Peptide turnover was always faster in the microlayer than in subsurface waters. This was confirmed by allowing a new surface film to form on subsurface water; hydrolysis was still faster in the new surface film. In a year-long study, we found the relative difference between turnover times in the surface film and subsurface waters to vary greatly with season. While rate constants of peptide hydrolysis were generally higher in both microlayer and bulk water samples in spring/summer than in fall/winter, the difference in activity between the two environments was greatest in winter. Enhanced hydrolysis in the sea surface microlayer is likely due to the greater concentrations of DOM in the microlayer. Seasonal changes in distribution of hydrolytic activity between surface film and subsurface water probably reflect seasonal variation in the mechanisms of DOM enrichment, which depend on water temperature, substance and energy fluxes across the water–air boundary, activity of aquatic organisms and other seasonal variables. 相似文献
18.
The dynamics of high molecular weight organic matter in marine systems are influenced by molecular conformation, interactions with surfaces and susceptibility to enzymatic hydrolysis, parameters that are difficult to observe experimentally. Here we use electron paramagnetic resonance spectroscopy (EPR) and spin-labeled (SL-) polysaccharides to monitor the sorption of SL-polysaccharides to natural sediment surfaces and to montmorillonite and to observe decreases in polysaccharide size due to enzymatic hydrolysis. SL-pullulan, SL-xylan and SL-maltoheptaose all sorbed rapidly to muddy sediments but not to sandy sediments. SL-pullulan and SL-maltoheptaose also both sorbed to montmorillonite; however, SL-pullulan reached substantially greater final surface loadings than did SL-maltoheptaose. Using EPR has the advantages of being rapid (spectra can be acquired in 100 seconds), non-destructive and functional in complex media, including sediment slurries, muddy water or other optically opaque samples, permitting investigation of the interactions between biomacromolecules, extracellular enzymes and mineral surfaces in aquatic environments. 相似文献
19.
Gordon T. Taylor Robert Thunell Ramon Varela Claudia Benitez-Nelson Mary I. Scranton 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(8):1266-1283
Ectohydrolase activities of suspended microbiota were compared to those associated with sinking particles (sed-POM) retrieved from sediment traps deployed in the permanently anoxic Cariaco Basin. In shore-based assays, activities of aminopeptidase, β-glucosidase, chitinase and alkaline phosphatase were measured in samples obtained from oxic and anoxic depths using MUF- and MCA-labeled fluorogenic substrate analogs. Hydrolysis potentials for these enzymes in the seston varied widely over the nine cruises sampled (8 Nov 1996–3 May 2000) and among depths (15–1265 m); from <10 to over 1600 nM d?1 hydrolysate released, generally co-varying with one another and with suspended particulate organic carbon (POC) and particulate nitrogen (PN). Hydrolytic potentials, prokaryotic abundances and POC/PN concentrations in sinking debris were 400–1.3×107 times higher than in comparable volumes of seawater. However when normalized to PN, hydrolytic potentials in sediment trap samples were not demonstrably higher than in Niskin bottle samples. We estimate that PN pools in sediment trap samples were turned over 2–1400 times (medians=7–26x) slower by hydrolysis than were suspended PN pools. Median prokaryotic growth rates (divisions d?1) in sinking debris were also ～150 times slower than for bacterioplankton. Hydrolytic potentials in surface oxic waters were generally faster than in underlying anoxic waters on a volumetric basis (nM hydrolysate d?1), but were not significantly (p>0.05) different when normalized to PN or prokaryote abundances. Alkaline phosphatase was consistently the most active ectohydrolase in both sample types, suggesting that Cariaco Basin assemblages were adapted to decomposing phosphate esters in organic polymers. However, phosphorus limitation was not evident from nutrient inventories in the water column. Results support the hypothesis that efficiencies of polymer hydrolysis in anoxic waters are not inherently lower than in oxic waters. 相似文献
20.
Abstract. In the callianassid shrimp Nihonotrypaea harmandi (Bouvier 1901), the trichomycete fungus Enteromyces callianassae Lichtwardt 1961 occurs exclusively on the foregut lining. The enzymes from both the shrimp and the fungus apparently hydrolyze certain nitrogen and carbon compounds in detritus. The activities of various proteases and carbohydrases contained in the foregut juice were compared between fungus-infected shrimps collected from a sandflat in Kyushu, Japan (51 % infection rate) and uninfected shrimps from a nearby sandflat. The concentration of enzymatically hydrolyzable amino acids (EHAA) in sediment liberated by the foregut juice with fungi was slightly lower than that by 0.1 mg·ml-1 proteinase-K and significantly higher than that by the foregut juice without fungi. In both foregut juices, substantial enzyme activities were recorded for proteinase(s), peptidases, amylase, cellulase and β-1,3-glucanase, and minimal ones for maltase and cellobiase. Of the commercial substrates examined, only in the case of the mixture of 16 kinds of dipeptides was a significantly higher enzyme activity in the foregut juice with fungi observed. In the process of EHAA liberation from sediment, peptidases secreted by the fungus most probably act as a supplement to the endogenous secretion by the shrimp. This may explain the higher shrimp growth rate recorded for the population with fungi. However, the significantly higher sediment EHAA concentration of the sandflat inhabited by this population versus the population without fungi could be another crucial factor explaining the site difference in shrimp growth rate. 相似文献