Abstract
1. A theory has been developed which describes the time course of exo-enzyme-catalyzed hydrolysis of linear high polymer substrates which is accompanied by a competitive inhibition by products. The theory predicts that there is a linear relationship between t/p and p, where p is the concentration of product at time t, and that the slope s of the plot of t/p versus p is proportional to the number-average molecular weight _??_Mn of the polymer substrate when a given amount of substrate is taken. Based on this proportionality between s and -Mn, a kinetic method was proposed to determine the number-average molecular weight of linear polymer substrate by using an exo-enzyme hydrolyzing the polymer.
2. The theory was applied to the hydrolytic reactions of various fractions of amylose of different degrees of polymerization catalyzed by crystalline exo-enzyme glue-amylase of Rhizopus delemar to determine the numberaverage molecular weights of the fractions. Good agreement was obtained between the .R. values determined by the kinetic method and those determined by osmotic pressure and reducing end-group measurements.
3. This method is especially useful for the determination of -Mn of linear high polymers having larger -Mn values for which conventional methods would fail to give reliable data. -Mn's over 1, 000, 000 for some amylose fractions could be determined.
The authors wish to acknowledge with gratitude Professor Juichiro Fukumoto and Dr. Yoshio Tsujisaka for their donation of crystalline glut-amylase. We are also greatly indebted to Dr. Takehiko Watanabe for his interest and helpful discussions, and to Messrs. Mutsufumi Kawai and Nobuhiko Okazaki for their technical assistance.
