【摘要】 用N-溴代琥珀酰亚胺（NBS）和N-乙基丁二酰亚胺（NEM）分别对A．4041α-淀粉酶的主要组分α－Ⅲ的色氨酸（TrP）残基和巯基进行修饰．结果表明，50％的Trp残基被NBS修饰，可使酶活力完全丧失；Ca2+和底物可减少修饰酶的失活；加Ca2+或底物后修饰酶的荧光强度较对照修饰酶有显著提高．表明Trp是催化必需基团，并与结合底物和Ca2+有关．用过量NEM修饰巯基，酶活力改变不大，表明巯基不是酶的催化必需基因，并对酶的热稳定性基本无影响．更多还原

【Abstract】 N-bromosuccinimide (NBS) and N-ethylmaleimide (NEM) were used to modify the trptophan(Trp) residues and sulfhydryl groups respectively in the main component α-Ⅲ of A. 4041 α-amylase. When 50%Trp residues were modified by NBS, the modification enzyme activity was completelylost. Ca2+ and substrate can prohibit from the activity loss of modified enzyme and improve the fluorescence intensity compared with the control of the modification enzyme. The results show that Trpgroups are catalytical necessary ones and concern with substrate and Ca2+. On adding excess amountsof NEM to modify SH, the enzyme activity had little change, which shows that SH groups are not thecatalytlc necessary groups. Experimental resu1ts show that SH groups have little influence on enzymethermostabllity.更多还原