Rosalia Balcazar-Orozco

Biosynthesis of polyuronides inMucor rouxii: Partial characterization of fucosyl transferase

Abstract Most of the fucosyl transferase activity from Mucor rouxii was detected in a crude membrane fraction. The enzyme transferred l -fucose from GDP-fucose to endogenous and exogenous acceptors. When crude membrane fractions were treated with neutral detergents such as Trition X-100 or Brij 36 T enzyme activity became dependent on exogenous acceptors such as mucoric acid or mucoran. Brij-treated membrane fractions showed maximum fucosyl transferase activity at pH 6.5, and at a temperature between 22 and 28°C. The cations Mn 2+ , Mg 2+ , Co 2+ , Zn 2+ , Fe 2+ , and Ca 2+ activated the enzyme about twofold. The former was slightly more stimulatory at 4 m M . Km for GDP-fucose was 10 μ M . Evidence was obtained that mucoric acid serves as acceptor for fucosyl moieties. Acid hydrolysis of the product synthesized from GDP-fuc by Brij-treated membrane fractions revealed fucose as the major radioactive sugar.