Hund H K, Bär G, Lingens F
Institut für Mikrobiologie der Universität Hohenheim, Bundesrepublik Deutschland.
Z Naturforsch C J Biosci. 1989 Sep-Oct;44(9-10):797-801. doi: 10.1515/znc-1989-9-1017.
Actinoplanes missouriensis utilizes arogenate as an intermediate in L-tyrosine biosynthesis, while no evidence of prephenate dehydrogenase was observed. Arogenate dehydrogenase has been partially purified by a five-step procedure. The enzyme requires NAD as cofactor. The Km values for NAD and arogenate are 0.2 mM and 0.15 mM, respectively. The molecular weight of arogenate dehydrogenase is about 68,000, and SDS gel electrophoresis indicates a composition of two identical subunits. The enzyme is not feedback inhibited by L-tyrosine and unaffected by L-phenylalanine, prephenate, phenylpyruvate, p-hydroxyphenylpyruvate or L-tryptophan. Arogenate dehydrogenase is quite sensitive to p-hydroxymercuribenzoate with 50% inhibition at 12.5 microM of the SH-specific reagent. The presence of malate in usually applied arogenate preparations is demonstrated and the consequence of an impure substrate on arogenate dehydrogenase studies is discussed.
密苏里游动放线菌利用莽草酸作为L-酪氨酸生物合成的中间体，而未观察到预苯酸脱氢酶的存在迹象。莽草酸脱氢酶已通过五步程序进行了部分纯化。该酶需要NAD作为辅因子。NAD和莽草酸的Km值分别为0.2 mM和0.15 mM。莽草酸脱氢酶的分子量约为68,000，SDS凝胶电泳表明其由两个相同的亚基组成。该酶不受L-酪氨酸的反馈抑制，也不受L-苯丙氨酸、预苯酸、苯丙酮酸、对羟基苯丙酮酸或L-色氨酸的影响。莽草酸脱氢酶对对羟基汞苯甲酸非常敏感，在12.5 microM的SH特异性试剂下有50%的抑制率。证明了通常使用的莽草酸制剂中存在苹果酸，并讨论了不纯底物对莽草酸脱氢酶研究的影响。
