Enzyme activity involved in glucose phosphorylation in two arbuscular mycorrhizal fungi: indication that polyP is not the main phosphagen

Enzyme activity involved in glucose phosphorylation, the first step of glycolysis and the pentose phosphate pathway (PPP), in the spores, extra- and intraradical hyphae of Glomus etunicatum and G. coronatum was measured to clarify the role of polyphosphate as a phosphagen. Hexokinase, which utilizes ATP as a phosphagen was active in the all components of both fungi, suggesting that glucose can be metabolized generally through glycolysis/PPP. Polyphosphateglucokinase-type activity, in which polyphosphate is utilized as a phosphagen, was detectable in the spores and intraradical hyphae of both fungi but negligible compared with that of hexokinase. Hexokinase and polyphosphateglucokinase-type activities were characterized and it seems likely that the apparent polyphosphateglucokinase activity can be attributed to broad substrate specificity of the hexokinase.