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. Polyphosphateglucakinase-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. (C) 2001 Elsevier Science Ltd. All rights reserved.