Abstract
The properties of extracellular, soluble and insoluble invertases in mycelium of Hymenoscyphus ericae an ericoid mycorrhizal fungus, were investigated. Soluble and insoluble acid invertases were more active in sucrose- compared with glucose-grown mycelium, whereas extracellular invertase activities were similar in both glucose- and sucrose-grown cultures. Acid (pH 5·5) and alkaline (pH 9·0) invertases were detected in soluble and insoluble fractions but extracellular activity was predominantly acid (pH 5·5). Insoluble alkaline invertase was released completely by freeze-thawing. Freeze-thawing and Triton X-100 released similar proportions of acid invertase from the wall (42 and 31% respectively). The K m values varied from 9·1 m m (extracellular acid invertase) to 139·3 m m sucrose (soluble alkaline invertase). Fructose inhibited soluble alkaline invertase completely but it competitively inhibited soluble acid invertase. Increased soluble acid invertase activity was demonstrated in endomycorrhizas compared with uninoculated roots of cranberry.
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