An enzyme synthesizing fructose 2,6-bisphosphate occurs in leaves and is regulated by metabolite effectors

Abstract

An enzyme catalyzing the ATP and fructose 6-phosphate-dependent synthesis of fructose 2,6-bisphosphate, a regulator of glycolysis and gluconeogenesis, has been identified and partially purified from plants, specifically the cytoplasmic fraction of spinach leaf parenchyma cells. The enzyme, designated fructose 6-phosphate, 2-kinase, showed no response to a protein phosphorylation system known to inhibit the corresponding enzyme in mammalian cells, but it responded strikingly to metabolite effectors (P i, an activator/PGA, an inhibitor) through changes in substrate affinity and maximal velocity. The observed pattern of regulation suggests a role for chloroplasts in controlling cytoplasmic carbon processing.