pH-dependent decarboxylation of 2-amino-3-ketobutyrate, the unstable intermediate in the threonine dehydrogenase-initiated pathway for threonine utilization.
pH-dependent decarboxylation of 2-amino-3-ketobutyrate, the unstable intermediate in the threonine dehydrogenase-initiated pathway for threonine utilization.
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DOI：
10.1006/bbrc.1993.1157
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发表时间：
1993-02
影响因子：
3.1
通讯作者：
J. P. Marcus;E. E. Dekker-E.
中科院分区：
文献类型：
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作者：
J. P. Marcus;E. E. Dekker-E.
2-氨基-3-酮丁酸可以通过L-苏氨酸脱氢酶的作用容易地酶促形成。用于测定该β-酮酸的半衰期的方便测定法通过其在2-氨基-3-酮丁酸CoA裂解酶催化下快速定量转化为甘氨酸（+乙酰CoA）来提供。使用该系统，我们发现2-氨基-3-酮基丁酸酯的半衰期随pH值变化，从pH 5.9时的8.6分钟变化到pH 11.1时的140分钟，产生理论滴定曲线，预测该中间体的α-氨基的pKa值为8.15。这些数据被认为是相关的讨论有关的苏氨酸脱氢酶/2-氨基-3-酮丁酸CoA裂解酶复合物在苏氨酸利用途径和5-氨基乙酰丙酸酯酶催化的反应，其中2-氨基-3-酮己二酸的机制方面。
2-Amino-3-ketobutyrate can be readily formed enzymatically by the action of L-threonine dehydrogenase. A convenient assay for determining the half-life of this beta-keto acid is afforded by its rapid and quantitative conversion to glycine (+ acetyl CoA), as catalyzed by 2-amino-3-ketobutyrate CoA lyase. Using this system, we have found the half-life of 2-amino-3-ketobutyrate varies with pH from 8.6 minutes at pH 5.9 to 140 minutes at pH 11.1 yielding a theoretical titration curve that predicts a pKa value of 8.15 for the alpha-amino group of this intermediate. These data are considered relevant to discussions pertaining to a threonine dehydrogenase/2-amino-3-ketobutyrate CoA lyase enzyme complex in the threonine utilization pathway and to mechanistic aspects of the 5-aminolevulinate synthase-catalyzed reaction where 2-amino-3-ketoadipate is involved.