Studies on Fungicides. XII. Relationships between Cell Wall Glycan Synthesis and Hydrolysis by Mycelial Enzymes on Cochliobolus miyabeanus

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The relationships between the cell wall glycan synthesis and hydrolysis by mycelial crude enzyme were studied. The crude enzyme indicated some hydrolytic activities to the synthesized β-glucan or chitin-like substance under the optimum conditions for respective glycan synthesis. The most of all enzyme activities were found in the microsomal fraction (glucan synthetase and chitin synthetase) and the soluble fraction (β-glucanase and β-N-acetylglucosaminidase). The activities of the β-glucan synthetase or chitin synthetase contained in microsomal fraction were not affected by addition of uridine diphosphate (UDP)-N-acetylglucosamine (into β-glucan synthetic system) or UDP-glucose (into chitin synthetic system). While the activities of the β-glucanase or β-N-acetylglu-cosaminidase contained in the soluble fraction were inhibited by addition of UDP-N-acetylglucosamine (into β-glucanase assay system) or UDP-glucose (into β-N-acetylglucosaminidase assay system). Therefore, when the mycelial crude enzyme was used as synthetase, it is evident that UDP-N-acetylglucosamine (precursor of chitin) in the β-glucan synthetic system of UDP-glucose (precursor of β-glucan) in the chitin-like substance synthetic system is not a stimulator of synthetase but an inhibitor of hydrolytic enzymes. The possible role of these phenomena at the time of cell wall growth was discussed.
1976-07-25