A bacterial glucoamylase degrading cyclodextrins. Partial purification and properties of the enzyme from a Flavobacterium species

Abstract

A Flavobacterium species has been isolated which produces a cyclodextrin-degrading glucoamylase. The inducible, cell-bound enzyme was purified about 10-fold to 75% purity in 57% yield. The action of the enzyme was studied with the main cyclodextrins (cyclohexaamylose, cycloheptaamylose and cyclooctaamylose) and with the typical glucoamylase substrates, respectively. The final degradation product with all the substrates was glucose. Small amounts of maltose, which could be detected in the course of cyclodextrin degradation, were hydrolyzed at a lower rate. V for cyclohexaamylase was found to be about 14-15 mumol glucose min-1 (mg pure protein)-1, the Km for cyclohexaamylose was 0.142 mM. Apparently the enzyme preferred shorter alpha-D-glucopyranosyl chains. Besides maltose, amylopectin and glycogen proved to be very poor substrates. Some properties of the enzyme have been described.