OCCURRENCE AND PROPERTIES OF ACID INVERTASE IN CULTURES OF BOTRYTIS-CINEREA

Three fractions of acid invertase (beta-fructofuranosidase; EC 3.2.1.26) were found to be associated with axenic cultures of Botrytis cinerea. Fraction A (soluble) was released by homogenising the mycelium in low-salt buffer and fraction B (salt-soluble) could be extracted from the cell debris with 1 M NaCl. A third fraction (C) remained associated with the mycelial pellet. The relative proportions of the individual forms depended on the stage of fungal development and, to some extent, the extraction conditions. Invertase activity appeared to be constitutive as indicated by its presence in ungerminated spores as well as in cultures with glucose as the sole carbon source. Fractions A and B of Botrytis invertase did not differ in their biochemical behaviour throughout isolation, the most prominent response being an extremely stable interaction with Concanavalin A (Con A). Deglycosylation with N-glycopeptidase F was successful in part only under conditions simultaneously shown to guarantee complete removal of the carbohydrate moiety from yeast invertase. We believe that the distinct affinity for Con A, which is to our knowledge not paralleled by the enzyme from higher plants, holds some promise for an operational approach to separate plant and fungal invertases in phytopathogenic associations involving Botrytis cinerea.