Biological action of phosphonate analogs of fructose 2,6-bisphosphate on enzymes from higher plants

AbstractTwo analogs of fructose 2,6-bisphosphate have been prepared, in which the phosphoryl group on the second carbon is replaced by a methylphosphonoyl or a phosphonoyl group. Both inhibited spinach leaf cytosolic fructose-1,6-bisphosphatase and activated potato tuber pyrophosphate:fructose-6-phosphate phosphotransferase. Their relative effectiveness depended on the enzyme, revealing differences in the fructose 2,6-bisphosphate binding sites on the two enzymes. Their relative effectiveness and their binding constants were the same when pyrophosphate:fructose-6-phosphate phosphotransferase was assayed in the forward and in the reverse direction. It is concluded that pyrophosphate:fructose-6-phosphate phosphotransferase possesses one type of fructose 2,6-bisphosphate binding site, and catalysis is modified in parallel in both directions as the activator concentration is altered. These results led to the reinterpretation of the role of pyrophosphate:fructose-6-phosphate phosphotransferase and fructose 2,6-bisphosphate in higher plants