Ivanov L L, Botvinik M M
Biokhimiia. 1976 Apr;41(4):619-29.
The course of stereospecific selection of nucleophilic compounds was studied in the reaction of acyl-enzymes interaction with razemic substrate-like nucleophiles, e.g. amino acid esters, by measuring optical rotation or incorporation of labelled D-compounds. It was shown that the acyl-enzymes are not responsible for the stereospecific selection of substrate-like nucleophiles. Since stereospecific selection of nucleophiles occurs in some chymotrypsin-catalyzed reactions, such selection may be produced by chymotrypsin till the formation of an acyl-enzyme compound with the substrate at the enzyme-inhibitor stage (or the Michaelis complex) with nucleophilic compounds. Even under the optimal conditions no absolute stereospecific selection of nucleophiles occurred, as was observed in case of a substrate (a donor of the acyl amino acid residue), undergoing degradation. An essential role of a specific site of nucleophile binding in the reactions of chymotrypsin-catalyzed peptide bond formation, is emphasized.
通过测量旋光度或标记D-化合物的掺入，研究了酰基酶与外消旋底物样亲核试剂（如氨基酸酯）相互作用反应中亲核化合物的立体特异性选择过程。结果表明，酰基酶对底物样亲核试剂的立体特异性选择没有作用。由于在一些胰凝乳蛋白酶催化的反应中会发生亲核试剂的立体特异性选择，这种选择可能是由胰凝乳蛋白酶产生的，直到在酶-抑制剂阶段（或米氏复合物）与亲核化合物形成与底物的酰基酶化合物。即使在最佳条件下，也没有像底物（酰基氨基酸残基供体）降解时那样发生亲核试剂的绝对立体特异性选择。强调了亲核试剂结合特异性位点在胰凝乳蛋白酶催化的肽键形成反应中的重要作用。
