Enriched preparations of chitin synthase were obtained from cell homogenates from Supvolegnia monoica. Chitin synthase was solubilized from a mixed membrane fraction by two successive digitonin treatments. Glycerol gradient centrifugation of the solubilized proteins separated the chitin synthase activity from the majority of proteins and from 8-1,3 and p-1,4 glucan synthases. The properties of chitin synthase from this Oomycete fungus are similar to those reported for the enzymes of ehitinous fungi. The solubilized enzyme catalysed the synthesis in vitvo of spindle-like crystals of chitin. Biophysical analysis (by electron and X-ray diffractornetry and infrared spectroscopy) demonstrated that the polymer synthesized in vitro was a-chitin. These results and those previously reported demonstrate unambiguously that chitin synthase and chitin are normal components of the cell wall of the cellulosic fungus S. munoica.

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Growth of three different anaerobic rumen fungi Neocallimastix frontalis, Piromonas communis and Sphaeromonas communis was assessed in vitro at regular intervals by measurements of protein and chitin content and of chitin synthase activity of the cell free extracts. Similar trends and a comparable amount of protein and chitin were observed in the three species. However, chitin synthase activity was higher in S. communis and contrary to the activity of the other two strains did not decrease after maximum enzyme activity was reached. There were positive correlations between chitin content, protein content and chitin synthase activity during the active growth phase of the fungi indicating that they could be confidently used to determine in vitro growth phase and biomass concentration.