Eun H M, Miles E W
Biochemistry. 1984 Dec 18;23(26):6484-91. doi: 10.1021/bi00321a033.
The alpha subunit of tryptophan synthase from Escherichia coli is inactivated by phenylglyoxal and by (p-hydroxyphenyl)glyoxal. The use of these chemical modification reagents to determine the role of arginyl residues in the alpha subunit of tryptophan synthase has been complicated by our finding that these reagents react with sulfhydryl groups of the alpha subunit, as well as with arginyl residues. Analyses of the data for incorporation of phenyl[2-14C]glyoxal, for inactivation, and for sulfhydryl modification in the presence and absence of indole-3-glycerol phosphate indicate that two sulfhydryl groups and one arginine are essential for the activity. Our finding that the substrate protects the single essential arginyl residue but not the two sulfhydryl groups is consistent with the observed kinetics of partial protection by substrate or by a substrate analogue, indole-3-propanol phosphate. In contrast to phenylglyoxal, (p-hydroxyphenyl)glyoxal modifies two to three sulhydryl groups that are not protected by indole-3-glycerol phosphate and modifies none of the arginyl residues that are modified by phenylglyoxal.
来自大肠杆菌的色氨酸合酶的α亚基会被苯乙二醛和（对羟基苯基）乙二醛灭活。我们发现这些化学修饰试剂不仅会与色氨酸合酶α亚基的精氨酰残基反应，还会与α亚基的巯基反应，这使得利用这些试剂来确定精氨酰残基在色氨酸合酶α亚基中的作用变得复杂。对在有无吲哚 - 3 - 磷酸甘油存在的情况下苯[2 - ¹⁴C]乙二醛的掺入、灭活及巯基修饰的数据进行分析表明，两个巯基和一个精氨酸对活性至关重要。我们发现底物能保护单个必需的精氨酰残基，但不能保护两个巯基，这与观察到的底物或底物类似物吲哚 - 3 - 磷酸丙酯的部分保护动力学一致。与苯乙二醛不同，（对羟基苯基）乙二醛会修饰两个至三个不受吲哚 - 3 - 磷酸甘油保护的巯基，且不会修饰被苯乙二醛修饰的任何精氨酰残基。
