D2O-ALANINE EXCHANGE-REACTIONS CATALYZED BY ALANINE RACEMASE AND GLUTAMIC PYRUVIC TRANSAMINASE
D2O-ALANINE EXCHANGE-REACTIONS CATALYZED BY ALANINE RACEMASE AND GLUTAMIC PYRUVIC TRANSAMINASE
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DOI：
10.1016/0006-291x(74)90387-8
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发表时间：
1974-01-01
影响因子：
3.1
通讯作者：
JOHNSTON, RB
中科院分区：
文献类型：
--
作者：
BABU, UM;JOHNSTON, RB
摘要D2 O（> 90%）中的NMR研究表明，丙氨酸消旋酶（5.1. 1.1.）来自B。枯草杆菌催化D-和L-丙氨酸的α-氢与D2 O的交换。谷氨酸丙酮酸转氨酶（2.6. 1.2.）和谷氨酸草酰乙酸转氨酶（2.6. 1.1.）催化L-丙氨酸的α和β氢交换。α氢和β氢的交换速率似乎是相同的数量级。转氨酶催化的交换被催化量的丙酮酸盐增强。L-丙氨酸的侧链更牢固地保持在转氨酶的活性位点，使得平面共轭系统可以延伸到包括α和β碳。本文提出了磷酸吡哆醛依赖性转氨酶作用的一种普遍机制，它扩展了Braunstein和Snell机制，使之包括了已研究的转氨酶对氨基酸β氢不稳定的结构。
Abstract NMR studies in D 2 O (> 90%) reveal that Alanine Racemase (5.1. 1.1.) from B. subtilis catalyzes the exchange of the α hydrogen of D-and L-alanine with D 2 O. Glutamic Pyruvic Transaminase (2.6. 1.2.) and Glutamic Oxaloacetic Transaminase (2.6. 1.1.) catalyze the exchange of α and β hydrogens of L-alanine. The rates of exchange of α and β hydrogens appear to be of the same order of magnitude. The transaminase catalyzed exchange is enhanced by catalytic amounts of pyruvate. The side chain of L-alanine is held more rigidly at the active site of transaminase so that the planar conjugated system can be extended to include the α and β carbons. A generalized mechanism is proposed for the action of pyridoxal phosphate dependent transaminases which extends Braunstein and Snell mechanism to include the structures which contribute to the labilization of β hydrogens of amino acids by the transaminases that have been studied.