两种α-葡萄糖苷酶的酶学性质及转苷作用

摘要

The hydrolytic and transglycosidational activities vary for differentα-transglucisidases derived from Aspergillus niger. These differences can affect their practical applications. Twoα-transglucosidases, Glu-A and Glu-B,were expressed in Pichia pastoris to investigate their enzymatic properties. Results showed that the optimum temperature for both α-transglucisidases Glu-A and Glu-B was 55,℃,with an optimum pH at 5 and 6,respectively. Studies of Glu-A and Glu-B with maltose as the substrate revealed significant differences in their transglycosidational activities in terms of the composition of their products,with Glu-A producing 51.04%oligosaccharide,15.79%isomaltose,31.41%panose,and 4.18%isomaltotriose versus corresponding products of 35.85%,16.71%,4.15%,and 15.85%generated by Glu-B.%来源于黑曲霉(Aspergillus niger)的不同α–葡萄糖苷酶，其对底物的水解和转苷活性均存在一定差异，影响了它们在实际生产中的应用．以甲醇毕赤酵母重组菌株分别表达的两种α–葡萄糖苷酶 Glu-A 和 Glu-B 为研究对象，分析了两种酶的酶学性质，结果表明Glu-A和Glu-B最适作用温度均为50,℃，最适pH分别为5和6．对底物麦芽糖的转苷作用研究表明，产物低聚异麦芽糖中各种糖的种类和比例差别较大，Glu-A 作用麦芽糖后的总低聚糖、异麦芽糖、潘糖和异麦芽三糖的生成率分别为51.04%、15.79%、31.41%和4.18%，而 Glu-B 作用麦芽糖后的总低聚糖、异麦芽糖、潘糖和异麦芽三糖的生成率分别为35.85%、16.71%、4.15%与15.85%．