Kleinman M J, Wilkinson A E, Wright I P, Evans I H, Bevan E A
School of Natural Sciences, Hatfield Polytechnic, Herts, U.K.
Biochem J. 1988 Jan 1;249(1):163-70. doi: 10.1042/bj2490163.
The extracellular glucoamylase from certain strains of Saccharomyces cerevisiae can be purified from culture medium by a simple chromatographic procedure. The native enzyme is heavily glycosylated and has an Mr of about 250,000, but gel filtration indicates the existence of oligomers of larger size. Dissociation yields a form of Mr about 70,000. The glucoamylase is rich in serine and threonine and in aspartic acid plus asparagine, and has a pI of 4.62 and a pH optimum of 4.5-6.5. The thermostability and resistance to denaturants of the yeast enzyme is compared with those of two other fungal glucoamylases. Kinetic data for the yeast enzyme and a variety of substrates is presented; the enzyme is particularly ineffective in cleaving alpha-(1----6)-glycosidic bonds.
来自某些酿酒酵母菌株的胞外葡糖淀粉酶可以通过简单的色谱方法从培养基中纯化出来。天然酶高度糖基化，分子量约为250,000，但凝胶过滤表明存在更大尺寸的寡聚体。解离产生一种分子量约为70,000的形式。该葡糖淀粉酶富含丝氨酸、苏氨酸、天冬氨酸和天冬酰胺，其等电点为4.62，最适pH为4.5 - 6.5。将酵母酶的热稳定性和对变性剂的抗性与另外两种真菌葡糖淀粉酶进行了比较。给出了酵母酶与多种底物的动力学数据；该酶在切割α-(1→6)-糖苷键方面特别无效。
