Bellion E, Tan F
Department of Chemistry, University of Texas, Arlington 76019-0065.
Biochem J. 1987 Jun 15;244(3):565-70. doi: 10.1042/bj2440565.
A study was made of the NAD+-dependent alanine dehydrogenase (EC 1.4.1.1) elaborated by the methylotrophic bacterium Pseudomonas sp. strain MA when growing on succinate and NH4Cl. This enzyme was purified 400-fold and was found to be highly specific for NH3 and NAD+; however, hydroxypyruvate and bromopyruvate, but not alpha-oxoglutarate or glyoxylate, could replace pyruvate to a limited extent. The Mr of the native enzyme was shown to be 217,000, and electrophoresis in SDS/polyacrylamide gels revealed a minimum Mr of 53,000, suggesting a four-subunit structure. The enzyme, which has a pH optimum of 9.0, operated almost exclusively in the aminating direction in vitro. It was induced by NH3 or by alanine, and was repressed by growth on methylamine or glutamate. It is suggested that this enzyme has two roles in this organism, namely in NH3 assimilation and in alanine catabolism.
对甲基营养型细菌假单胞菌属MA菌株在琥珀酸盐和氯化铵上生长时所产生的NAD⁺依赖性丙氨酸脱氢酶（EC 1.4.1.1）进行了研究。该酶被纯化了400倍，发现它对NH₃和NAD⁺具有高度特异性；然而，羟基丙酮酸和溴丙酮酸，而不是α-酮戊二酸或乙醛酸，在一定程度上可以替代丙酮酸。天然酶的Mr为217,000，在SDS/聚丙烯酰胺凝胶中的电泳显示最小Mr为53,000，表明其具有四亚基结构。该酶的最适pH为9.0，在体外几乎完全以氨基化方向起作用。它由NH₃或丙氨酸诱导，并在甲胺或谷氨酸上生长时受到抑制。有人认为这种酶在该生物体中具有两个作用，即在NH₃同化和丙氨酸分解代谢中。
