嗜热芽孢杆菌丙氨酸脱氢酶的调控与功能

Regulatory control and function of alanine dehydrogenase from a thermophilic bacillus.

作者信息

Epstein I, Grossowicz N

出版信息

Biochim Biophys Acta. 1976 Oct 11;445(3):549-57. doi: 10.1016/0005-2744(76)90109-1.

Abstract

L-alanine dehydrogenase, (L-alanine:NAD+ oxidoreductase (deaminating), EC 1.4.1.1) synthesis in a thermophilic bacillus was found to be subjected to regulatory control. Addition of L- and D-alanine and L-serine to cultures growing in the presence of either succinate or pyruvate, induced an accelerated synthesis of the alanine dehydrogenase enzyme. Synthesis of the enzyme was dependent on the presence of inducer during growth and was arrested by addition of glucose. Catabolite repression by glucose was abolished by limiting the ammonium concentration during growth. The apparent Km values of the substrates involved in alanine dehydrogenase activity are as follows (M): NH4+, 4-10(-2); pyruvate, 5-10(-4); NADH, 6-10(-5); L-alanine, 3.1-10(-3) and NAD, 2-10(-4). Alanine dehydrogenase activity was measurable at temperatures below the minimal growth temperature (at 25 degrees C) and the highest activity was found at 65 degrees C; heat denaturation occurred at 80 degrees C.

摘要

已发现嗜热芽孢杆菌中L-丙氨酸脱氢酶（L-丙氨酸：NAD⁺氧化还原酶（脱氨基），EC 1.4.1.1）的合成受到调控。在以琥珀酸盐或丙酮酸盐为碳源生长的培养物中添加L-丙氨酸、D-丙氨酸和L-丝氨酸，会诱导丙氨酸脱氢酶的合成加速。该酶的合成在生长期间依赖于诱导剂的存在，添加葡萄糖会使其合成停止。通过在生长期间限制铵浓度，可消除葡萄糖的分解代谢阻遏作用。参与丙氨酸脱氢酶活性的底物的表观Km值如下（M）：NH₄⁺，4×10⁻²；丙酮酸盐，5×10⁻⁴；NADH，6×10⁻⁵；L-丙氨酸，3.1×10⁻³；NAD，2×10⁻⁴。在低于最低生长温度（25℃）时可检测到丙氨酸脱氢酶活性，在65℃时活性最高；80℃时发生热变性。