IDENTIFICATION OF 2 ALPHA-GLUCOSIDASE ACTIVITIES IN CLOSTRIDIUM-ACETOBUTYLICUM NCIB-8052

Maltose metabolism in the obligate anaerobe Clostridium acetobutylicum was studied. The sugar is accumulated via an energy-dependent transport process which is not a phosphotransferase. Cell extracts were incapable of phosphorylating maltose in the presence or absence of phosphoenolpyruvate or ATP, but exhibited hydrolytic activity against a range of glucoside substrates. The activity was predominantly in the soluble fraction of cell extracts, indicating a cytoplasmic location in the cell. Gel filtration on Sephadex G100 indicated the presence of at least two alpha-glucosidases. One enzyme (maltase) was active with maltose and maltotriose, while the other (pNPGase) hydrolysed isomaltose and several glucoside analogues, but neither showed activity against starch. Both glucosidases were induced by isomaltose, maltose, glucose and starch, but not by xylose, sucrose or cellobiose. In the presence of both glucose and maltose, growing cells showed a preference for glucose, apparently due to regulation of maltose transport, which did not occur in glucose-grown cells.