黑曲霉S_4生淀粉糖化酶纯化组分的性质及其动力学常数

Properties and Kinetic Constants of Purified Fractions of Raw-Starch-Digesting Glucoamylases from Asp. niger S_4

生淀粉糖化酶是可以水解生淀粉的葡萄糖糖化酶(Ec3.2.1.3,α-1.4-糖苷酶),它是近代工业中极为重要的酶类之一。虽然对生淀粉糖化酶可水解淀粉中所有的D-糖苷键已经清楚,由单糖逆合成寡糖的动力学研究也比较深入,但有关它对各种常用生淀粉材料的水解动力学以及各生淀粉糖化酶组分之间的相互关系的研究却很少。本研究通过在不同温度和pH下,生淀粉糖化酶的三个组分对寡糖和各种生淀粉作用的动力学常数。

Three enzymes being homogeneous in polyacrylamide gel electrophoresis from Aspergillus niger S4 were studied. They were proved to be glucoamylases by the paper chromatography and the determination of optical rotation. Kinetic studies on the enzymes revealed that their Km values for high-molecular-weight subctrates differed from low-molecular-weight ones. With the increasing of substrates'chain length, Km values decreased while Vmax increased. Thus it resulted in Vmax/Km values' increasing, i.e. digesting ability of enzymes on substrates was increased. From the star pattern of their amino acid composition, it showed that the original relation of three enzymes were very closed.