(2R,3S)-3-Vinylmalic acid (VM) was designed as a mechanism-based inhibitor of threo-3-isopropylmalate dehydrogenase (LPMDH), the rate-determining enzyme responsible for the penultimate step in the biosynthetic pathway of the essential amino acid L-leucine. The synthesis of VM was achieved in six steps from diethyl (R)-malate. Besides its weak activity as a substrate, VM was shown to be a mechanism-based inhibitor (K-I = 1.20 mM) for IPMDH as deduced from the time-dependent and kinetic analyses. 2-Oxo-3-pentenoate was identified as the enzyme reaction product of VM by GCMS analysis and H-1 NMR spectroscopy, but the supplemented 2-oxo-3-pentenoate was not, in contrast, inhibitive to the enzyme reaction. It seems likely from these results that an activated or nucleophilic amino acid of IPMDH by deprotonation during the ordinary enzyme reaction process participates in a strong interaction with the 2-oxo-3-pentenoate product, probably by the formation of a transient covalent bond, which in turn gives rise to inhibition of the enzyme reaction.
(S)-3-
乙烯基苹果酸(V M)被设计为苏式-3-异丙基
苹果酸脱氢酶(LPMDH)的机制性
抑制剂,该酶是必需
氨基酸L-亮氨酸生物合成途径倒数第二步的限速酶。VM的合成以(R)-
苹果酸二
乙酯为原料,经过六步反应制得。除了具有弱的底物活性外,VM被认为是机制性
抑制剂(KI=1.20m M)。该结论由时间依赖性和动力学分析得出。通过气相色谱-质谱分析和H-1核磁共振光谱鉴定,2-氧代-
3-戊烯酸被确定为VM的酶反应产物,但补充的2-氧代-
3-戊烯酸并未表现出抑制作用。从上述结果可推测,在日常酶反应过程中,
IPMDH通过去质子化生成活性或亲核
氨基酸,与2-氧代-
3-戊烯酸产物形成强相互作用,很可能是通过生成瞬时共价键,从而抑制酶反应。