MECHANISM OF D-CYCLOSERINE ACTION - ALANINE RACEMASE FROM ESCHERICHIA-COLI W
MECHANISM OF D-CYCLOSERINE ACTION - ALANINE RACEMASE FROM ESCHERICHIA-COLI W
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DOI：
10.1128/jb.110.3.978-987.1972
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发表时间：
1972-01-01
影响因子：
3.2
通讯作者：
NEUHAUS, FC
中科院分区：
文献类型：
--
作者：
LAMBERT, MP;NEUHAUS, FC
抗生素环丝氨酸是一种有效的丙氨酸消旋酶抑制剂。由于缺乏环丝氨酸对金黄色葡萄球菌丙氨酸消旋酶的抑制作用，Roze和Strominger提出了环丝氨酸假说。这个假设认为d-环丝氨酸具有酶表面底物所需的构象，而l-环丝氨酸不具有这种构象。对大肠杆菌的丙氨酸外消旋酶进行了研究，以确定这些观察结果是否为所有丙氨酸外消旋酶的一般特征。该酶（分子量= 95000）的Michaelis-Menten常数分别为4.6 × 10−4和9.7 × 10−4mford-和l-丙氨酸。vmax与通行费方向的比值为2.3。根据霍尔丹关系计算出的平衡常数为1.11±0.15。2 -环丝氨酸和1 -环丝氨酸都是竞争性抑制剂，其常数（Ki）分别为6.5 × 10−4和2.1 × 10−3m。kmd -丙氨酸与kid -环丝氨酸的比值为0.71，kml -丙氨酸与ki -环丝氨酸的比值为0.46。由于环丝氨酸是一种有效的抑制剂，因此环丝氨酸假说不适用于me酶。coliW。
The antibioticd-cycloserine is an effective inhibitor of alanine racemase. The lack of inhibition byl-cycloserine of alanine racemase fromStaphylococcus aureusled Roze and Strominger to formulate the cycloserine hypothesis. This hypothesis states thatd-cycloserine has the conformation required of the substrates on the enzyme surface and thatl-cycloserine cannot have this conformation. Alanine racemase fromEscherichia coliW has been examined to establish whether these observations are a general feature of all alanine racemases. The enzyme (molecular weight = 95,000) has Michaelis-Menten constants of 4.6 × 10−4mand 9.7 × 10−4mford- andl-alanine, respectively. The ratio ofVmaxin thed- tol-direction is 2.3. The equilibrium constant calculated from the Haldane relationship is 1.11 ± 0.15. Bothd- andl-cycloserine are competitive inhibitors with constants (Ki) of 6.5 × 10−4mand 2.1 × 10−3m, respectively. The ratio ofKmd-alanine toKid-cycloserine is 0.71, and the ratio ofKml-alanine toKil-cycloserine is 0.46. Sincel-cycloserine is an effective inhibitor, it is concluded that the cycloserine hypothesis does not apply to the enzyme fromE. coliW.