The reaction of N-bromosuccinimide with enolase

Ten tryptophan residues per one protein molecule were found to be present in the enolase from human and swine muscle. In Tris buffer, N-bromosuccinimide (NBS) inactivated the enolases after oxidation of all 10 tryptophan residues. The presence of 2-phosphoglycerate (2-PGA) partially protected the activity, and in the presence of 2-PGA together with Mg2+ full protection was observed. In phosphate buffer, only 6 tryptophan residues could be oxidized, but the enzyme was fully inactivated. 2-PGA made possible the oxidation of all 10 tryptophan residues, concomitant with full inactivation. In either case, Mg2+ had no effect. The Km values and pH optima were the same for the native and partially NBS-modified enolases.