枯草芽胞杆菌L-天冬氨酸a脱羧酶的酶学性质

Characterization of L-aspartate-a-decarboxylase from Bacillus subtilis

摘要:

b-丙氨酸是一种重要的医药化工原料，目前主要依靠化学法进行生产。探寻更为环保和高效的生物生产法是未来研究的一个方向。L-天冬氨酸a脱羧酶 (PanD) 能特异地脱去L-天冬氨酸的a羧基，生成b-丙氨酸。本文比较了3种分别来源于大肠杆菌、谷氨酸棒状杆菌及枯草芽胞杆菌的PanD比酶活 (分别为0.98、7.52和8.4 U/mg)。后两者的最适pH均为6.5，最适反应温度分别为65 ℃及60 ℃。与目前研究最多的来源于大肠杆菌和谷氨酸棒状杆菌的PanD相比，来源于枯草芽胞杆菌的PanD具有更好的活性和热稳定性，具有更强的工业应用潜力。同时，本文对该酶特有的翻译后自剪切及机理性失活现象进行了分析和讨论。

Abstract:

As an important material in pharmaceutical and chemical industry, b-alanine was mainly produced by chemical methods. L-aspartate-a-decarboxylase could catalyze the a-decarboxylation from L-aspartate to b-alanine. Determinations for specific activities of PanDs from Escherichia coli, Corynebacterium glutamicum and Bacillus subtilis were performed in this study (0.98 U/mg, 7.52 U/mg and 8.4 U/mg respectively). The optimal temperature and pH of PanDs from C. glutamicum and B. subtilis were 65 °C, pH 6.5 and 60 °C, pH 6.5 respectively. According to our research, PanD from B. subtilis could be more appropriate for industrial application because of the higher activity and thermostability when compared to PanDs from E. coli and C. glutamicum which had been the most studied. We also analyzed and discussed the special post-translation self-cleavage phenomenon and the mechanism based inactivation.