Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
Biochemistry. 2012 Jul 3;51(26):5226-8. doi: 10.1021/bi300569r. Epub 2012 Jun 22.
Burst-phase kinetic analysis was used to evaluate the deamination rate of the aminated-methylidene imidazolone (NH(2)-MIO) adduct of a Taxus phenylalanine aminomutase. The kinetic parameters were interrogated by a non-natural substrate (S)-styryl-α-alanine that yielded a chromophoric styrylacrylate product upon deamination by the aminomutase. Transient inactivation of the enzyme by the NH(2)-MIO adduct intermediate resulted in an initial burst of product, with reactivation by deamination of the adduct. This study validated the rate constants of a kinetic model demonstrating that the NH(2)-MIO adduct and cinnamate intermediate are sufficiently retained to catalyze the natural α- to β-phenylalanine isomerization.
采用爆发式动力学分析方法评估 Taxus 苯丙氨酸氨甲酰基转移酶的氨甲基烯亚胺（NH(2)-MIO）加合物的脱氨速率。通过非天然底物（S）-苯乙烯基-α-丙氨酸来检测动力学参数，该底物通过氨甲酰基转移酶脱氨生成发色性苯乙烯基丙烯酸盐产物。酶被 NH(2)-MIO 加合物中间体瞬时失活会导致产物的初始爆发，通过加合物的脱氨进行再激活。这项研究验证了动力学模型的速率常数，表明 NH(2)-MIO 加合物和肉桂酸中间体能足够保留以催化天然的α-到β-苯丙氨酸异构化。
