Duedahl-Olesen L, Kragh K M, Zimmermann W
Department of Civil Engineering, Aalborg University, Denmark.
Carbohydr Res. 2000 Oct 20;329(1):97-107. doi: 10.1016/s0008-6215(00)00153-1.
Bacillus clausii BT-21 produced an extracellular malto-oligosaccharide-forming amylase active at high pH when grown on starch substrates. The enzyme was purified to homogeneity by affinity and anion-exchange chromatography. The molecular weight of the enzyme estimated by sodium dodecyl sulfate polyacrylamide electrophoresis was 101 kDa. The enzyme showed an optimum of activity at pH 9.5 and 55 degrees C. Maltohexaose was detected as the main initially formed starch hydrolysis product. Maltotetraose and maltose were the main products obtained after hydrolysis of starch by the enzyme for an extended period of time and were not further degraded. The enzyme readily hydrolysed soluble starch, amylopectin and amylose, while cyclodextrins, pullulan or dextran were not degraded. The mode of action during hydrolysis of starch indicated an exo-acting type of amylolytic enzyme mainly producing maltohexaose and maltotetraose. Amino acid sequencing of the enzyme revealed high homology with the maltohexaose-forming amylase from Bacillus sp. H-167.
克劳氏芽孢杆菌BT-21在以淀粉为底物生长时，会产生一种在高pH值下具有活性的胞外形成麦芽寡糖的淀粉酶。通过亲和色谱和阴离子交换色谱将该酶纯化至同质。经十二烷基硫酸钠聚丙烯酰胺凝胶电泳估计，该酶的分子量为101 kDa。该酶在pH 9.5和55℃时表现出最佳活性。麦芽六糖被检测为最初形成的主要淀粉水解产物。在酶对淀粉进行长时间水解后，麦芽四糖和麦芽糖是主要产物，且不再进一步降解。该酶能轻易水解可溶性淀粉、支链淀粉和直链淀粉，而环糊精、支链淀粉或葡聚糖则不会被降解。淀粉水解过程中的作用模式表明这是一种主要产生麦芽六糖和麦芽四糖的外切型淀粉酶。该酶的氨基酸测序显示与芽孢杆菌属H-167形成麦芽六糖的淀粉酶具有高度同源性。
