Uridine diphosphate glucose breakdown is mediated by a unique enzyme activated by fructose 2,6-bisphosphate in Solanum tuberosum

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Abstract
In the presence of Pi, UDP glucose (UDPG) is specifically hydrolyzed to glucose 1-phosphate and UDP by a unique enzyme, UDPG phosphorylase. The activity of the enzyme was maximally stimulated by fructose 2,6-bisphosphate, a regulatory metabolite recently discovered in both plants and animals, and by 2-phosphoglyceric acid. At 1 .mu.M, fructose 2,6-bisphosphate stimulated UDPG phosphorolysis 10-fold, whereas 2-phosphoglyceric acid was required at higher concentrations (100 .mu.M) to produce a similar effect. Fructose 2,6-bisphosphate appears to increase the affinity of the enzyme for Pi, with a change in Km from 1.6 to 0.3 mM. Apparently, fructose 2,6-bisphosphate participates in the regulation of other pathways of carbohydrate metabolism in addition to playing its recognized role in glycolysis gluconeogenesis.