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羟化酶是细菌降解烷烃的关键酶,本文以南极低温降解菌Shewanella sp.NJ49为研究对象,通过硫酸铵沉淀、超滤浓缩及葡聚糖凝胶Sephadex G-75柱层析方法,分离纯化NJ49的羟化酶,获得了单一羟化酶组分,研究了温度、p H、表面活性剂和盐度等环境因素对NJ49羟化酶酶活活性影响。结果表明,羟化酶组分由α、β、γ三个亚基组成,分子质量分别为56,45和36 k D。NJ49最适产酶条件为:温度15℃、p H7.2、盐度55;不同类型表面活性剂对酶的活性影响效应不一,两性离子表面活性剂、阳离子表面活性剂、非离子表面活性剂对酶活没有作用,阴离子表面活性剂+非离子表面活性剂混和剂和阳离子表面活性剂+非离子表面活性剂混和剂能提高羟化酶的活性。 相似文献
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本研究预测naa cluster中的naaB基因负责催化烟酸到6-羟基烟酸的反应。通过对NaaB的蛋白序列进行分析,发现该酶含有三个亚基,分别由naaBL1、naaBS、naaBL2基因编码,其中naaBL1和naaBL2分别编码2个含有钼辅因子结合结构的大亚基,naaBS基因编码一个含有[2Fe-2S]簇的小亚基。本研究对naaB基因进行了克隆,将构建的重组质粒pME6032-naaBL1SL2分别转化到无色杆菌(Achromobacter sp.)和大肠杆菌(Escherichia coli)中,通过HPLC和LC-MS检测验证了NaaB负责催化烟酸到6-羟基烟酸,并且在无色杆菌和大肠杆菌中NaaB均能够转化烟酸,这与之前报道烟酸羟化酶不能在大肠杆菌表达的结果不同,说明NaaB的基因编码和催化功能具有独特性。通过序列分析推测NaaB的这一特性可能跟该酶同时含有两个钼结合结构域的大亚基有关。 相似文献
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We have shown previously that exposure of Atlantic croaker to a PCB mixture (Aroclor 1254) results in impaired reproductive neuroendocrine function. In addition, we have identified hypothalamic tryptophan hydroxylase (TPH), the rate-limiting enzyme in serotonin (5-hydroxytryptamine) synthesis, as a target of PCB neuroendocrine toxicity. In order to further elucidate the mechanisms of PCB neurotoxicity, the present study investigated whether PCB-induced decrease in hypothalamic TPH activity resulted from degradation of the enzyme protein. Fish were exposed to Aroclor 1254 in the diet (0.1 mg/100 g body weight (BW)/day) for 30 days. The PCB exposure elicited a significant decrease in hypothalamic TPH protein content, which could be at least partially responsible for the reduced TPH activity. To test whether a similar PCB exposure could cause oxidative damage in croaker hypothalamic tissues, we examined the formation of malondialdehyde (MDA) protein adducts as a marker of lipid peroxidation (LPO). The same dose of PCB increased the MDA-protein adduct formation in the hypothalamus. In a separate experiment, the role of vitamin E, an antioxidant, to prevent or decrease the effect of PCB on hypothalamic TPH activity and gonadal growth was examined. The vitamin E co-treatments (1 and 10 mg/100 g BW/day) with PCB significantly reduced the effects of PCB on TPH activity and gonadal growth. These results suggest possible involvement of oxidative processes in PCB neurotoxicity. 相似文献
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