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从常见的黑海参 Aplysia kurodai 中分离和表征两种褐藻胶裂解酶同工酶,AkAly28 和 AkAly33。

Isolation and characterization of two alginate lyase isozymes, AkAly28 and AkAly33, from the common sea hare Aplysia kurodai.

机构信息

Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan.

出版信息

Comp Biochem Physiol B Biochem Mol Biol. 2010 Dec;157(4):317-25. doi: 10.1016/j.cbpb.2010.07.006. Epub 2010 Aug 11.

Abstract

Two alginate lyase isozymes, AkAly28 and AkAly33, with approximate molecular masses of 28 and 33kDa, respectively, were isolated from the digestive fluid of the common sea hare, Aplysia kurodai. Both of AkAly28 and AkAly33 were regarded as the endolytic polymannuronate (poly(M)) lyase (EC 4.2.2.3) since they preferably degraded poly(M)-rich substrate producing unsaturated tri- and disaccharides and rapidly decreased the viscosity of sodium alginate solution in the initial phase of degradation. Optimal pH and temperature of the two enzymes were similarly observed at pH 6.7 and 40°C, respectively. Temperature that caused a half inactivation of the two enzymes during 20-min incubation was also similar to each other, i.e., 38°C. However, NaCl requirement and activity toward oligosaccharide substrates of the two enzymes were significantly different from each other. Namely, AkAly28 showed practically no activity in the absence of NaCl and the maximal activity at NaCl concentrations higher than 0.2 M, whereas AkAly33 showed ~20% of maximal activity despite the absence of NaCl and the maximal activity at around 0.1 M NaCl. AkAly28 hardly degraded oligosaccharides smaller than tetrasaccharide, while AkAly33 could degrade oligosaccharides larger than disaccharide producing disaccharide and 2-keto-3-deoxy-gluconaldehyde (an open chain form of unsaturated monosaccharide). Analysis of the N-terminal and internal amino-acid sequences of AkAly28 and AkAly33 indicated that both of the two enzymes belong to polysaccharide lyase family 14.

摘要

从黑海参消化液中分离得到两种褐藻胶裂解酶同工酶 AkAly28 和 AkAly33,其分子量约为 28 和 33kDa。AkAly28 和 AkAly33 均被认为是内切聚甘露糖醛酸(poly(M))裂解酶(EC 4.2.2.3),因为它们优先降解富含 poly(M)的底物,产生不饱和三糖和二糖,并在降解的初始阶段迅速降低海藻酸钠溶液的粘度。两种酶的最适 pH 和温度均相似,分别为 pH6.7 和 40°C。在 20min 孵育过程中导致两种酶半数失活的温度也相似,即 38°C。然而,两种酶对盐的需求和对寡糖底物的活性有显著差异。即,AkAly28 在没有 NaCl 的情况下几乎没有活性,在 NaCl 浓度高于 0.2M 时具有最大活性,而 AkAly33 即使在没有 NaCl 的情况下也具有约 20%的最大活性,在约 0.1M NaCl 时具有最大活性。AkAly28 几乎不能降解小于四糖的寡糖,而 AkAly33 可以降解二糖以上的寡糖,产生二糖和 2-酮-3-脱氧葡萄糖醛酸(不饱和单糖的开链形式)。AkAly28 和 AkAly33 的 N 末端和内部氨基酸序列分析表明,这两种酶均属于多糖裂解酶家族 14。

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