REGULATION OF ENDO-1,4-BETA-GLUCANASE SECRETION FROM TERMITOMYCES-CLYPEATUS BY CARBON CATABOLIC PRODUCT(S)

Secretion of CMCase by Termitomyces clypeatus was only observed in the presence of a gluconeogenic amino acid, a citrate-cycle acid, maleate , subinhibitory concentrations of glucosamine, or fluoride in the medi um. The enzyme was not secreted in the presence of caffeine or IBMX or theophylline, and these phosphodiesterase inhibitors lowered the secr etion of CMCase by glutamate. The presence of both glucosamine and glu tamate in a cellulose medium were, however, antagonistic to CMCase sec retion. In a growth medium, xylose and glucose were equivalent carbon source for the fungus while succinate was a poor source and strongly r epressed growth at higher concentrations. Growth of T. clypeatus was h ighly favored in media containing xylose/glucose with succinate/glutam ate. During growth of T. clypeatus in a glucose medium, the intracellu lar glucose level was stabilized by the presence of succinate, glutama te or glucosamine in the medium. All these observation suggested that a negative cellular regulation, mediated by carbon catabolic product(s ), existed in T. clypeatus which regulated the secretion of CMCase. A transient but significant increase of intracellular cAMP and cGMP leve ls was observed at the onset of mycelial growth in glucose and glucose /maleate media, respectively.