Biosynthesis of chitosan in membrane fractions from Mucor rouxii by the concerted action of chitin synthetase and a particulate deacetylase

Abstract

Mixed membrane fractions from Mucor rouxii synthesize two different products when incubated with uridine diphosphate N-acetylglucosamine: one containing an average of 2200–3000 N-acetylglucosamine units (chitin), and a second one of about equal size containing, in addition to N-acetylglucosamine, a large proportion of glucosamine units (chitosan). Biosynthesis of both polymers requires chitin synthetase, but biosynthesis of the second, partially deacetylated product also requires the action of a membrane-bound deacetylase. The deacetylase was absent from purified chitosomes and chitosomal subunits. Evidence was obtained that during chitosan biosynthesis, chain formation and deacetylation occur simultaneously. It is hypothesized that the role of the membrane-bound deacetylase activity is to initiate the deacetylation of a proportion of nascent chitin chains which may be thus recognized by an extracellular soluble deacetylase responsible for their further deacetylation.