BIOCHEMICAL, GENETIC, AND REGULATORY STUDIES OF ALANINE CATABOLISM IN ESCHERICHIA-COLI-K12
BIOCHEMICAL, GENETIC, AND REGULATORY STUDIES OF ALANINE CATABOLISM IN ESCHERICHIA-COLI-K12
复制标题
DOI：
10.1007/bf00332894
复制
发表时间：
1976-01-01
期刊：
影响因子：
--
通讯作者：
VENABLES, WA
中科院分区：
文献类型：
--
作者：
FRANKLIN, FCH;VENABLES, WA
E.ColiK12利用D-和L-丙氨酸立体异构体作为生长所需的唯一C、N和能量来源。这种能力完全依赖于具有活性的膜结合D-丙氨酸脱氢酶，并被该酶缺陷的突变体所丧失。该酶以D-丙氨酸为底物的Km值为30 mM，最适pH为apprx。8.9.D-丙氨酸是活性最高的底物，L-丙氨酸没有活性，其他几种D-氨基酸的活性是D-丙氨酸的10-50%。D-丙氨酸的氧化通过含有细胞色素的呼吸链与O2相连。D-丙氨酸或L-丙氨酸可诱导脱氢酶的合成16~23倍，但只有D-丙氨酸具有内在的诱导活性。L丙氨酸只有在不受抑制的丙氨酸外消旋酶存在的情况下才能作为底物或诱导剂发挥活性，该酶能将其转化为D-异构体。它们的结构基因在Ara和Leu之间的定位以及其他相似性表明，D-丙氨酸脱氢酶和Wijsman的丙氨酸酶是同一酶。D-丙氨酸和L-丙氨酸都是丙氨酸外消旋酶的诱导剂。D-丙氨酸脱氢酶和丙氨酸消旋酶的合成受分解代谢抑制的调节。
E. coli K12 utilized D- and L-stereoisomers of alanine as sole sources of C, N and energy for growth. This capability was absolutely dependent upon the possession of an active membrane-bound D-alanine dehydrogenase, and was lost by mutants in which the enzyme was defective. The Km for the enzyme with D-alanine as substrate was 30 mM, and the pH optimum .apprx. 8.9. D-Alanine was the most active substrate; L-alanine was inactive, and several other D-amino acids were 10-50% as active as D-alanine. Oxidation of D-alanine was linked to O2 via a cytochrome-containing respiratory chain. Synthesis of the dehydrogenase was induced 16 to 23-fold by incubation with D- or L-alanine, but only D-alanine was intrinsically active as an inducer. L-Alanine was active as a substrate or inducer only in the presence of an uninhibited alanine racemase which converted it to the D-isomer. The map-location of their structural genes between ara and leu, together with other similarities, indicate that D-alanine dehydrogenase and the alaninase of Wijsman are the same enzyme. Both D- and L-alanine were intrinsically active as inducers of alanine racemase synthesis. The synthesis of D-alanine dehydrogenase and alanine racemase was regulated by catabolite repression.