产碱菌麦芽四糖淀粉酶的底物特异性  

Substrate Specificity of Maltotetraose-forming Amylase from an Alcaligenes sp.

作　　者：朱静[1] 严自正[1] 周健[1] 梁改芹[1] 张树政[1] 

机构地区：[1]中国科学院微生物研究所

出　　处：《生物化学与生物物理学报》1995年第6期663-669,共7页

基　　金：中国科学院资助

摘　　要：产碱菌Ｇ４Ａ仅能水解由α－１，４－葡萄糖苷键连接的麦芽寡糖、淀粉或糖原。淀粉和糖原的水解产物为Ｇ４；麦芽寡糖Ｇ５，Ｇ６和Ｇ７的水解产物分别为Ｇ４＋Ｇ、Ｇ４＋Ｇ２和Ｇ４＋Ｇ３，水解速度为Ｇ５＜Ｇ６＜Ｇ７。直链淀粉的水解限度为１００％，其他淀粉为６０～７４％，糖原仅３４％，表明该酶为从麦芽寡糖、淀粉或糖原非还原末端顺序切割第４个ａ－１，４－葡萄糖苷键的外切型淀粉酶。Ｇ４Ａ对Ｇ５、Ｇ６、Ｇ７及直链淀粉、可溶性淀粉、糯米淀粉、支链淀粉、糖原、糊精的Ｋｍ值分另为１．１５６、０．９２６、０．８７７ｍｍｏｌ／Ｌ及３．２８、３．２、３．１、２．８．２．４２、３．９２ｍｇ／ｍｌ，Ｖｍａｘ值分别为１９６１、１５３８５、１７８５７及４３９９０、２９８２２、２９３６２、２３５８２、１４６１５、３２０２０ｍｇＧ４·ｈ－１·ｍｐ－１。A maltotetraoae - forming amylase from Alcaligenes sp. hydrolyzed only the a1, 4-glucosidic linkages of maltooligosaccharides, starch or glycogen. The product of starch glycogen hydrolyzed by G4 A was G4; Hydrolysis products of G5, G6,and G7 were G4 + G, G4 + G2 and G4+G3 respectively, and their rate of hydrolysis was G5<G6<G7. The degree of hydrolysis of amylose was 100%, that of various starch, 60￣74%, while that of glycogen only 34%. It was concluded that G4A was an exo-amylase which cleaved the fourth bond from the non-reducing end of maltooligosaccharides, starch or glycogen. The Km values of G4A for G5, G6, G 7and amylose, soluble starch, glutinous rice starch, amylopectin, glycogen, dextrin were l.156, 0.926, 0.877 mM and 3.28, 3.2, 3.1, 2.8, 2.42, 3 .29 mg/ml respectively; The Vmax values of G4A for the above substrates were 1961, 15385, 17857 and 43990, 29822, 29362, 23582, 14615, 32020 mgG4·h-1·mg-1 respectively.

关 键 词：产碱菌 麦芽四糖淀粉酶 底物特异性 

分 类 号：Q939.106[生物学—微生物学]