SYNTHESIS IN-VITRO OF CRYSTALLINE CHITIN BY A SOLUBILIZED ENZYME FROMTHE CELLULOSIC FUNGUS SAPROLEGNIA-MONOICA

Enriched preparations of chitin synthase were obtained from cell homog enates from Saprolegnia monoica. Chitin synthase was solubilized from a mixed membrane fraction by two successive digitonin treatments. Glyc erol gradient centrifugation of the solubilized proteins separated the chitin synthase activity from the majority of proteins and from beta- 1,3 and beta-1,4 glucan synthases. The properties of chitin synthase f rom this Oomycete fungus are similar to those reported for the enzymes of chitinous fungi. The solubilized enzyme catalysed the synthesis in vitro of spindle-like crystals of chitin. Biophysical analysis (by el ectron and X-ray diffractometry and infrared spectroscopy) demonstrate d that the polymer synthesized in vitro was alpha-chitin. These result s and those previously reported demonstrate unambiguously that chitin synthase and chitin are normal components of the cell wall of the cell ulosic fungus S. monoica.