FRUCTOSE-1,6-BISPHOSPHATASE IN STAGE-VI FROG OOCYTES - EVIDENCE FOR AN ACTIVE ENZYME IN-VIVO

The characterization of fructose-1,6-bisphosphatase in stage VI oocyte s from the frog Caudiverbera caudiverbera, as well as the in vivo acti vity, is reported. The enzyme has a subunit molecular weight of approx imately 43,500, has an apparent K-m value of 17 mu M for fructose-1,6- bisP, and is inhibited by substrate concentrations beyond 100 mu M. AM P and fructose-2,6-bisP are strong inhibitors of oocyte fructose-1,6-b isphosphatase activity with K-i values of 9 and 2 mu M respectively. I nhibition by AMP is cooperative with a n(H) value of 2.2. In vivo fruc tose-1,6-bisphosphatase activity was demonstrated by microinjection of [U-C-14]- or [6-P-32]fructose-1,6-bisP and subsequent chromatographic separation and identification of labeled products. The relevance of t hese findings for the metabolism of glucose in frog oocytes is discuss ed. (C) 1995 Academic Press, Inc.