Mannosyltransfer reactions in rabbit liver microsomes

Rabbit liver microsomes catalyzed mannosyltransfer from GDP-[14C]mannose to free D -mannose resulting in the synthesis of α-1,2-, α-1,3-, and α-1,6-mannosyl-mannose. Whereas formation of α-1,2-mannosyl-mannose was stimulated by the addition of manganese chloride or nickel chloride and was inhibited by EDTA, synthesis of α-1,3-mannosyl-mannose was unaffected by manganese or EDTA and was inhibited by nickel. Formation of α-1,6-mannosyl-mannose appeared to be stimulated by manganese and inhibited by nickel. These results suggest that three different mannosyltransferases were involved in the synthesis of mannosyl-mannose glycosidic linkages in rabbit liver.