Kochhar S, Dua R D
Biochem Biophys Res Commun. 1985 Jan 31;126(2):966-73. doi: 10.1016/0006-291x(85)90280-3.
Liquefying alpha-amylase from Bacillus amyloliquefaciens was inactivated on treatment with N-bromosuccinamide. Preincubation of the enzyme with either of the substrate, or competitive inhibitor provided significant protection against inactivation. The relationship between activity loss and the number of tryptophan residues modified, as well as presence of substrate/inhibitor in the reaction mixture, demonstrated that only one of three modifiable tryptophan residues is at or near the active center. The apparent Km of the modified enzyme for soluble starch increased manifold, thus implicating the sensitive tryptophan residue in the substrate binding region of the enzyme.
解淀粉芽孢杆菌产生的液化型α-淀粉酶在用N-溴代琥珀酰胺处理后失活。该酶与底物或竞争性抑制剂进行预孵育可提供显著的抗失活保护作用。活性丧失与被修饰的色氨酸残基数量之间的关系，以及反应混合物中底物/抑制剂的存在情况表明，三个可修饰的色氨酸残基中只有一个位于活性中心或其附近。修饰后的酶对可溶性淀粉的表观Km值增加了数倍，因此表明该敏感的色氨酸残基位于酶的底物结合区域。
