Mobilization of granulose in Clostridium pasteurianum. Purification and properties of granulose phosphorylase

1. The granulose of Clostridium pasteurianum ATCC 6013 is degraded when the organism is incubated in a medium containing no utilizable source of carbon and energy. 2. Mobilization of the polyglucan does not occur in the presence of exogenous glucose. 3. Breakdown of granulose is effected by a constitutively synthesized alpha-1,4-polyglucan phosphorylase. 4. Partial (530-fold) purification of this granulose phosphorylase was facilitated by its being loosely bound to the native granules of its substrate polyglucan. 5. The enzyme (pH optimum 6.4) was assayed both (a) in the degradative direction, K(m) for P(i)=2.2mm, and (b) in the synthetic direction, K(m) for glucose 1-phosphate=0.05mm. No requirement for bivalent cations was evidenced. 6. Granulose phosphorylase was inhibited by various nucleotide sugars; GDP-glucose, ADP-glucose (K(i)=20mum) and UDP-glucose (K(i)=60mum) were particularly potent competitive inhibitors. ATP, NADP(+) and NADPH (at 1mm) were less effective inhibitors, whereas AMP was slightly stimulatory. 7. It would appear that granulose mobilization is favoured under conditions of low adenylate energy charge, but is prevented under conditions of ;glucose excess' chiefly by ADP-glucose-mediated inhibition of granulose phosphorylase.