Formation of α-1,2- and α-1,3-linked mannose disaccharides from dolichyl mannosyl phosphate by rat liver membrane enzymes

Abstract

Dolichyl mannosyl phosphate and GDPmannose were active substrates for the transfer of mannose to methyl-α- d-mannose, p-nitrophenyl-α- d-mannose, and free mannose with rat liver microsomal membranes. The products formed during dolichyl mannosyl phosphate incubation with methyl-α- d-mannose or with mannose were α-linked. The dissaccharides formed by incubation of dolichyl mannosyl phosphate or GDPmannose with mannose were identified by paper chromatography and electrophoresis as mannose-α-1,2-mannose and mannose-α-1,3-mannose. Synthesis of each product was dependent on the assay conditions used and was most markedly affected by the presence of detergent. Transfer of mannose from either substrate to form mannose-α-1,3-mannose was severely inhibited by Triton X-100.