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J Gen Microbiol. 1993 Dec;139(12):3071-8.

Characterization of the 1,3-beta-glucan synthase of Aspergillus fumigatus.

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Unité de Mycologie, Institut Pasteur, Paris, France.


1,3-beta-Glucan synthase activity has been detected in a membrane fraction extracted from the mycelium of the filamentous fungus Aspergillus fumigatus. The enzyme was solubilized by CHAPS and stabilized by filtration on a Bio-gel P30 column. Highest activity was obtained in the early exponential phase of growth. Four factors--GTP, NaF, sucrose and EDTA--added during the extraction procedure, were essential for optimal 1,3-beta-glucan synthase activity. The soluble enzyme preparation was photolabelled with 5-azido-[32P]UDP-glucose and 5-125IASA-UDP-glucose which bind covalently to the enzyme after UV irradiation. These UDP-glucose substrate analogues were competitive inhibitors of the enzyme with a Ki of 1.42 mM and 0.3 mM for 5-azido-UDP-glucose and 5-ASA-UDP-glucose, respectively (Km for UDP-glucose = 1.9 mM). Potential UDP-glucose-binding polypeptides were identified with molecular masses of 31, 50 and 115 kDa.

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