Long lifetimes of β-glucosidase,leucine aminopeptidase,and phosphatase in Arctic seawater |
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| Authors: | Andrew D Steen Carol Arnosti |
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| Institution: | 1. Scientific Research Center for Ecological Safety Russian Academy of Sciences, Korpusnaya 18, St. Petersburg 197110, Russia;2. Zoological Institute of the Russian Academy of Sciences, Universitetskaya Embankment 1, St. Petersburg 199034, Russia;3. Saint Petersburg State University of Aerospace Instrumentation, Bolshaya Morskaya 67, St. Petersburg 190000, Russia;1. Canada Research Chair on the Geochemistry of Coastal Hydrogeosystems, Université du Québec à Rimouski, Rimouski, Québec G5L3A1, Canada;2. Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, Québec G5L3A1, Canada;1. Department of Marine Sciences and Convergent Technology, Hanyang University, Ansan 15588, Republic of Korea;2. Now at Department of Botany, University of Allahabad, Allahabad 211002, India;3. School of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang 37673, Republic of Korea;4. South Sea Research Institute, Korea Institute of Ocean Science and Technology, Geoje 53201, Republic of Korea;5. Now at Arctic Research Center, Korea Polar Research Institute, Incheon 21990, Republic of Korea;6. Division of Polar Ocean Environment, Korea Polar Research Institute, Incheon 21990, Republic of Korea |
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| Abstract: | 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. |
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