Properties of mannosyl- and N-acetylglucosamine-1-phosphate transferases towards dolichol phosphate in liver microsomes from pig embryos.

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.

Biosynthesis of lipid-linked oligosaccharides in embryonic liver. Glucosylation of mannose containing dolichyl diphosphate oligosaccharide.

A maximum rate of dolichyl phosphate [14C]glucose synthesis from 55-day embryos was achieved at 16 nM concentration of exogenous dolichyl phosphate and exceeded about 3 times that without addition of dolichyl phosphate. The highest values of [14C]glucose incorporation from UDP-[14C]glucose into dolichyl phosphate [14C]glucose, dolichyl diphosphate [14C]Glc-oligosaccharides and protein were reached at 5 min time point of incubation of liver microsomes both from embryos and sows. The radioactive incorporation into proteins was about 7-fold higher in liver microsomes from sows compared to that from embryos, probably due to the greater content of acceptor proteins in microsomes from sows.

Biosynthesis of lipid-linked oligosaccharides by microsomes from virus induced Hepatoma MC-29. Dependence of some glycosyl transferases on dolichyl phosphates of different chain length.

Dolichyl phosphates of various chain length ranging from 7 to 22 isoprene units were tested as lipid acceptors in transglycosylation reactions in chicken liver and Hepatoma MC-29. In the presence of exogenous dolichyl phosphate mixture (18 and 19 isoprene units) the synthesis of dolichyl pyrophosphate N-acetylglucosamine and dolichyl phosphate mannose increased 3 times both in the liver and Hepatoma MC-29, while the formation of dolichyl phosphate glucose was 4 fold higher in the liver and 6-fold higher in Hepatoma MC-29. In liver microsomes the maximum rate of the stimulation of glycosylation was achieved by exogenous dolichyl phosphates, containing 18 and 19 isoprene units, while glycosyl transferases in microsomes from Hepatoma MC-29 did not show any structural requirements to the chain length of dolichyl phosphates.

Biosynthesis of lipid-linked oligosaccharides in embryonic liver. Formation of mannose containing derivatives.

In the presence of exogenous dolichyl phosphate mannosyl transferase activity towards dolichyl phosphate was nearly 3-fold higher in microsomes from pig embryonic liver compared to that from adult liver. After incubation of microsomes from embryonic liver with UDP-N-acetylglucosamine and GDP-[14C]mannose lipid-linked tri- to undecasaccharides were discovered in CHCl3-CH3OH (2:1, v/v) and CHCl3-CH3OH-H2O (1:1:0.3, by vol) extracts.