| 摘要 |
PURPOSE: To obtain the subject new enzyme having a specific amino acid sequence, acting on polysaccharides and maltooligo saccharide containing α-1,4- glycoside bonds, good in thermal stability and stability in an alkaline pH region, and useful for producing maltose for infusion solutions, foods, etc. CONSTITUTION: The new recombined β-amylase has an amino acid sequence containing an amino acid sequence of the formula, acts on α-1,4-glucan to successively release β-maltose from the non-reduced end, acts on polysaccharides having α-1,4-glycoside bonds, such as soluble starch, amylose and amylopectin and maltooligosaccharide having a polymerization degree of >=3, is optimal in a pH region of 3.5-7.0, is stable in a pH region of 3.5-12.0, is optimal at a temperature of 65 deg.C at pH of 7.0, is stable at temperatures up to 62.5 deg.C for 30 min at a pH of 7.0 in the absence of a substrate. The enzyme is obtained by site-specifically mutating amino acids at the 181, 291, 293, 346, 347, 348, 672 positions of the amino acid sequence of barley β-amylase in a genetic level and subsequently expressing the gene by a genetic engineering method. |
