Glycogen accumulation under gluconeogenic conditions in Mucor rouxii: Effects of cycloheximide

Abstract

Mucor rouxii can efficiently use sugar or gluconeogenic substrates as sources of carbon. Under both culture conditions significant amounts of glycogen were accumulated in the mycelium. After transfer to fresh media of different carbon composition, rapid changes in the polysaccharide level were observed. These changes can be used as a useful parameter to evaluate the in vivo status of carbon metabolism, i.e., showing that the M. rouxii capacity for glycogen synthesis and degradation is contitutive, whereas gluconeogenic metabolism requires adaptation. Cycloheximide largely stimulated glycogen accumulation in mycelia adapted to gluconeogenesis, but not in glucose-grown mycelia, which was devoid of gluconeogenic activity. The antibiotic appeared to preferentially stimulate gluconeogenesis, probably by increasing the endogenous amino acid pool. The effect of cycloheximide might represent a potential tool to study the control of gluconeogenesis in the intact cell system.