【摘要】 淀粉水解酶广泛用于淀粉加工业中，何秉旺等在选育产耐热β-淀粉酶菌株中得到一株坚强芽孢杆菌（Bacillusfirmus）725，该菌株产生的淀粉酶有较好的热稳定性，水解淀粉的主要产物为麦芽糖。自然菌株产生的淀粉酶往往是多种淀粉酶的混合，为进一步研究该菌株产生的淀粉酶的性质和在工业上应用的可能性，分离了三个淀粉酶基因，在大肠杆菌中克隆和表达[1]。其中重组质粒pBA150产生的淀粉酶的淀粉水解产物主要是麦芽糖［1］。β-淀粉酶（EC.3．2.1．2）水解淀粉的主要产物是麦芽糖，工业上可用于生产高麦芽糖浆，近年来又有β-淀粉酶用于啤酒工业的报道[2]。本文报道重组质粒pBA150的β-淀粉酶基因的序列分析及推导出的氨基酸序列同己知β-淀粉酶的氨基酸序列比较。更多还原

【Abstract】 The gene encoding a β-amylase from Bacillus firmus 725 was sequenced.The sequenced DNA of 2012 bp contains one open reading frame of 1406 nucleotides without a translation stop codon. The deduced amino acid sequence homology with those known bacterial and some plant β-amylase was 98% for Bacillus polymyxa 72,98% for Bacillus polymyxa ATCC8523, 82% for Bacillus circulans, 54% for Clostridium thermosulfurogenes, 49% for Bacillus cereus BQ10-S1, 50% for Bacillus cereus var. mycoides, 36% for barley, and 36% for soybeen Eleven well-conserved regions were found among the amino acid sequences of the nine β-amylases.更多还原