title: Properties of mannosyl- and N-acetylglucosamine-1-phosphate transferases towards dolichol phosphate in liver microsomes from pig embryos.
abstract: 1. The activity of mannosyl- and N-acetylglucosamine-1-phosphate transferases in microsomes from pig embryonic liver was linear to 1 min of incubation at 37 degrees C. 2. The activity of both enzymes was higher in the presence of Mg2+ as compared to Mn2+. A maximal stimulatory effect of Mn2+ was obtained at 2 mM concentration and greater concentrations of it inhibited the activities of both enzymes. 3. The activity of mannosyl transferase was found to be highest after treatment of microsomes with Nonidet P-40 while the activity of N-acetylglucosamine-1-phosphate transferase was greatest in the presence of sodium deoxycholate. 4. The Km for acceptor substrate was 1.6 x 10(-5)M in the reaction for dolichol phosphate mannose synthesis and 2.2 x 10(-5)M in the reaction for dolichol pyrophosphate N-acetylglucosamine formation. 5. The Km for GDP-mannose was 1.4 x 10(-5)M and for UDP-N-acetylglucosamine-6.2 x 10(-5)M. At saturating concentrations of donor substrates V values (pmol/min/mg) were 1330 and 150, respectively.
authors.affiliation: Institute of General and Comparative Pathology, Bulgarian Academy of Sciences, Sofia.
authors.forename: V I
authors.initials: VI
authors.lastname: Zhivkov
authors.forename: S V
authors.initials: SV
authors.lastname: Kyosseva
authors.forename: B N
authors.initials: BN
authors.lastname: Panayotov
authors.forename: Z N
authors.initials: ZN
authors.lastname: Kyossev
mesh_terms: D000818:Animals; D004288:Dolichol Phosphates / Q000378:metabolism*; D004622:Embryo, Mammalian; D006602:Hexosyltransferases / Q000378:metabolism*; D007700:Kinetics; D008364:Mannosyltransferases / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology*; D010770:Phosphotransferases / Q000378:metabolism*; D011106:Polyisoprenyl Phosphates / Q000378:metabolism*; D013552:Swine; D017855:Transferases (Other Substituted Phosphate Groups)
chemical_list: D004288:Dolichol Phosphates; D011106:Polyisoprenyl Phosphates; D006602:Hexosyltransferases; D008364:Mannosyltransferases; C022755:dolichyl-phosphate beta-D-mannosyltransferase; D010770:Phosphotransferases; D017855:Transferases (Other Substituted Phosphate Groups); C023222:UDPacetylglucosamine-dolichyl-phosphate acetylglucosamine-1-phosphate transferase