Differential effects of bromination on substrates and inhibitors of kynureninase from Pseudomonas fluorescens
作者:Christian Heiss、Jay Anderson、Robert S. Phillips
DOI:10.1039/b208910f
日期:2003.1.13
inhibitors of kynureninase from Pseudomonas fluorescens. Both 3-bromo-L-kynurenine and 5-bromo-L-kynurenine were found to be substrates with similar k(cat) values to L-kynurenine, but the K(m) value for 3-bromo-L-kynurenine is very high (ca. 2 mM) compared to that for 5-bromo-L-kynurenine (11 microM) and L-kynurenine (25 microM). Both isomers of bromokynurenine react with kynureninase within the dead
合成了一系列溴化化合物,并评估了它们作为荧光假单胞菌犬尿氨酸酶的底物和抑制剂。发现3-溴-L-犬尿氨酸和5-溴-L-犬尿氨酸都是具有与L-犬尿氨酸相似的k(cat)值的底物,但是3-溴-L-犬尿氨酸的K(m)值非常高与5-溴-L-犬尿氨酸(11 microM)和L-犬尿氨酸(25 microM)相比要高(大约2 mM)。溴尿肾上腺素的两个异构体在停止流仪器的死时间(约1毫秒)内与尿尿氨酸酶反应,形成最大波长为494 nm的醌型中间体,其降解速率常数为300-600 s-1,与L相似。 -犬尿氨酸。还制备了5-溴二氢-L-犬尿氨酸的两种非对映异构体,它们是比二氢-L-犬尿氨酸更有效的抑制剂。(4R)-5-溴二氢-L-犬尿氨酸是迄今发现的最有效的荧光假单胞菌犬尿氨酸酶抑制剂(Ki = 55 nM),也可作为慢速底物;另一方面,(4S)-受体没有显示可测量的底物活性,但是它是有效的竞争性抑制剂,Ki值为170