大豆籽粒尿囊素酶的变性和化学修饰

Denaturation and chemical modification of allantoinase from fresh soybean seeds

大豆籽粒尿囊素酶对十二烷基磺酸钠、尿素、盐酸胍变性处理较不敏感．十二烷基磺酸钠、尿素变性处理的尿囊素酶可通过稀释而恢复活力，但一经盐酸胍变性后却难以通过稀释而恢复活力．酶蛋白质氨基酸残基化学修饰结果表明，巯基、赖氨酸残基、酪氨酸残基不是构成酶分子活力中心的必需基团，色氨酸残基是酶活性中心的必需基团．甘油醛、异烟肼不影响酶反应，而乙酰氧肟氧肟酸抑制酶活力３９．６％

Some properties of allantoinase from fresh soybean seeds were investigated. The enzyme was not sensitive to sodium dodecyl sulfate, urea or granidine·HCl treatments. However, the enzyme could be reversibly denatured by sodium dodecyl sulfate and urea but irreversibly denatured by guanidine·HCl. DL Glyceraldehyde (0￣25 mmol·L -1 ), Isoniazid (10 mmol·L -1 ) did not affect enzymatic reaction. Acetohydroxamate (25 mmol·L -1 ) inhibited 39.6% of the enzymatic activity. The chemical modification of the enzyme was studied. The results suggested that thiol groups, lysyl residues and tyrosyl residues be non essential for the enzyme activity. And the results also indicated that tryptophyl residues were essential for the enzyme catalytic activity and located at the active site of the enzyme molecule.