Kopczynski M G, Babior B M
J Biol Chem. 1984 Jun 25;259(12):7652-4.
Ethanolamine ammonia-lyase is an adenosylcobalamin-dependent enzyme that catalyzes the rearrangement of ethanolamine and other vicinal amino alcohols to oxo-compounds and ammonia. Treatment of this enzyme with the sulfhydryl group-blocking reagent methyl methanethiosulfonate produces a species with diminished catalytic activity. When methyl methanethiosulfonate -treated ethanolamine ammonia-lyase was incubated with a carboxyl-blocking reagent consisting of glycine ethyl ester plus a water-soluble carbodiimide, the enzyme lost more than 80% of its residual activity, while at the same time glycine ethyl ester was incorporated into it at a stoichiometry of 6 mol/mol of enzyme. Both the loss of activity and the incorporation of glycine ethyl ester were prevented if ethanolamine was included in the glycine ethyl ester-containing incubation mixture. These results suggest that an active site carboxyl group plays a role in the mechanism of catalysis by ethanolamine ammonia-lyase, and that this carboxyl group is amidated when the enzyme is incubated with glycine ethyl ester plus carbodiimide.
乙醇胺氨裂解酶是一种依赖腺苷钴胺素的酶，它催化乙醇胺和其他邻氨基醇重排为氧代化合物和氨。用巯基阻断试剂甲硫氨酸甲酯处理该酶会产生催化活性降低的物种。当用甲硫氨酸甲酯处理的乙醇胺氨裂解酶与由甘氨酸乙酯加水溶性碳二亚胺组成的羧基阻断试剂一起温育时，该酶失去了超过80%的残余活性，同时甘氨酸乙酯以每摩尔酶6摩尔的化学计量比掺入其中。如果在含有甘氨酸乙酯的温育混合物中加入乙醇胺，则活性的丧失和甘氨酸乙酯的掺入都会被阻止。这些结果表明，活性位点羧基在乙醇胺氨裂解酶的催化机制中起作用，并且当该酶与甘氨酸乙酯加碳二亚胺一起温育时，这个羧基会被酰胺化。
