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Solubilization and properties of polyprenyl phosphate: GDP-d-mannose mannosyl transferase

1979; Elsevier BV; Volume: 198; Issue: 1 Linguagem: Inglês

10.1016/0003-9861(79)90401-6

1096-0384

P.L. Carlo, C. L. Villemez,

Polysaccharides and Plant Cell Walls

Abstract A soluble enzyme which catalyzes the formation of dolichyl β- d -mannosyl phosphate has been prepared from encysting cultures of Acanthamoeba castellanii . The enzyme is relatively specific for GDP- d -mannose in that GDP- d -glucose and various uridine nucleotides do not serve as substrates. Uridine diphosphate d -glucose is not an inhibitor at 100-fold molar excess concentration, but GDP- d -glucose, GDP, and GMP do inhibit the reaction at relatively high concentrations. The apparent K m for GDP- d -mannose is approximately 0.25 μ m and that for dolichyl phosphate is approximately 3.3 μ m . The enzyme has a pH optimum of 7.0, a temperature optimum of 27 °C, and requires a divalent cation. Magnesium, cobalt, and manganese salts will serve as cofactors but maximum activity is produced by Mn 2+ . No loss of activity is evident after storage for 2 weeks at −70 °C, but half the activity was lost within 3 days at 0 °C, and a third of the activity was lost within 2 weeks at −20 °C.