摘要
在不引起酶变性的条件下,用半胱氨酸(Cys)专一性化学修饰试剂碘乙酸、对氯汞苯甲酸(?)(CMB),5,5′-二硫双硝基苯甲酸(DTNB)对酶分子进行化学修饰后,酶活性显著下降。发现酶的失活程度与修饰剂浓度间存在着化学计量关系,同时底物(酪蛋白)对酶活性有明显的保护作用。说明被修饰的部位(Cya残基)是酶的活性中心基团。Cys对酶有明显的激活作用;同时,(?)CMB、DTNB、碘乙酸对酶活性有明显的抑制作用(?)CMB抑制或O_2氧化而失活的酶溶液,又可被Cys重新激活,而恢复其活力,进一步证明其活性中心存在着Cys残基。以上事实均与典型的植物巯基蛋白酶——木瓜蛋白酶一致,说明番麻蛋白酶是一种巯基蛋白醇,其活性中心存在着Cys。
A proteinase that hydrolyzed caicin was isolated from leaves of Apoos (?) and the functional group at in active aite was determined by chemical modification metbods.It was found that the activity of the protednase was activated by cysteins and inhibited by sulfhydryl reagents,such as iodoacetic add (DTNB).These inhibitions were protected by its subatrate casein,indicating that the group modified by these reagents was at the active site of the enzyme.The activity of the inhibited enzyme by pCMB was reactived by cysteine.The activity of the enzyme solution kept at room temperature decreased gradually to about 33% at the fourth day and could be reactived to 80% of its original activity by cysteine.All the above resultes came to the conchision that the proteinase from leaveaf Agave (?) was a aulfhydryl proteinase.
出处
《华南农业大学学报》
CAS
CSCD
1992年第2期61-66,共6页
Journal of South China Agricultural University
