THE ACTIVITY OF THE GLUCONATE-H-POMBE CELLS IS DOWN-REGULATED BY D-GLUCOSE AND EXOGENOUS CAMP( SYMPORTER OF SCHIZOSACCHAROMYCES)

Schizosaccharomyces pombe cells take up D-gluconate, as an alternative carbon source for growth, during glucose starvation or when cultured on glycerol-containing medium, Gluconate uptake is not detectable whil e cells are growing logarithmically on glucose. The addition of D-gluc ose as well as its non-metabolizable analogues to glycerol-grown cells causes an immediate loss of gluconate transport within 1 min. The rev ersible down-regulation of the gluconate carrier occurs after glucose has been internalized. This regulation is triggered not only by D-gluc ose but also by extracellular cAMP even in the absence of the cAMP-dep endent protein kinase (PKA1).