【摘要】 用PMSF、TNBS、NBS、DTNB及溴代乙酸在一定条件下分别选择性地作用于缢蛏两种碱性磷酸酯酸(AKPⅠ和AKPⅡ)的Ser、Lys、Trp、His及巯基,并对酶活力的变化和吸收光谱的变化作了相应的测定。结果表明,PMSF、TNBS和NBS的修饰能显著抑制AKPⅠ和AKPⅡ的活力,活力的降低与修饰剂的浓度有关;溴代乙酸和DTNB对AKPⅠ和AKPⅡ的活力不表现抑制作用。我们初步认为,Ser、Lys和Trp残基可能是AKPⅠ和AKPⅡ的活力必需基团。AKPⅠ的TNBS失活动力学研究还表明一个Lys践基是AKPⅠ表现催化活力所必需的。更多还原

【Abstract】 Two forms of alkaline phosphatasc from Sinonovacula constricta (AKP Ⅰ& AKP Ⅱ ) were selectively modified by PMSF, TNBS, NBS, bromoacetic acid and DTNB and the changes in their activities and absorption spectra have been studied.It was found that the reaction of AKP Ⅰ and AKP Ⅱ with PMSF, TNBS and NBS resulted in a strong inhibition of enzyme activities. In the presence of 5mM PMSF) the inactivation process appeared to be of the first order reaction and the rate constants were measured to be 1.85×10-4sec-1. and 2.00×10-4sec-1. for AKP Ⅰ and AKP Ⅱ respectively. On reacting with TNBS or NBS, the catalytic activities of AKP Ⅰ and AKP Ⅱ decreased steadily with the increase of modifier concentration. Kinetic studies of inactivation of AKP by chemical modification demonstrated that Lys and Trp residues are essential for the activities of AKP Ⅰ and AKPⅡ and one of the Lys residuesis situated in the active site of AKP 1111111111. It has also been shown that His residue and SH group are indifferent to the activities of AKP Ⅰ and AKP Ⅱ.更多还原