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 transpo rt process which is not a phosphotransferase. Cell extracts were incap able of phosphorylating maltose in the presence or absence of phosphoe nolpyruvate 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 c ell. Gel filtration on Sephadex G100 indicated the presence of at leas t 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 starc h. Both glucosidases were induced by isomaltose, maltose, glucose and starch, but not by xylose, sucrose or cellobiose. In the presence of b oth glucose and maltose, growing cells showed a preference for glucose , apparently due to regulation of maltose transport, which did not occ ur in glucose-grown cells.