[Purification and properties of low molecular weight endoglucanase of the cellulase complex from Trichoderma koningii]

Abstract

A homogenous low molecular weight 1,4-beta-glucan glucanohydrolase (endoglucanase) has been isolated from a crude commercial preparation of cellokoningine P10X of T. koningii origin. The molecular weight of the enzyme as determined by polyacrylamide gel electrophoresis is 13 000. The endoglucanase was obtained as a lyophylized preparation free of the cellobiase activity. It was shown that cellobiose or methylcellobioside activate the effect of the low molecular weight endoglucanase (measured by the viscometric technique with respect to CMC hydrolysis) and at the same time almost completely suppress the activity of high molecular weight endoglucanases from the sane source. A detailed kinetic study of the effects showed that the low molecular weight enzyme is activated by a transglycosylation mechanism, where cellobiose acts as an added nucleophile. The activation is 6-fold at saturating concentrations of cellobiose (Ks = 15 mM). It was shown that diverse kinetic behaviour of cellobiose which can act both as activatory and inhibitor for endoglucanases from different sources can be explained, firstly, by different ratios of low to high molecular weight endoglucanases in the cellulase complexes, and, secondly, by their ability to catalyze transglycosylation reactions, which, in turn, results in a transfer of reducing end groups of the reaction products onto cellobiose as an added nucleophile.