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Changes in the accumulation of two types of α-D-galactosides: raffinose family oligosaccharides and galactosyl pinitols were compared with changes in the activities of galactosyltransferases during winter vetch (Vicia villosa Roth.) seed development and maturation. Occurrence of galactinol and raffinose in young seeds and changes in activities of galactinol synthase and raffinose synthase during seed development indicated that formation of raffinose oligosaccharides (RFOs) preceded synthesis of galactopinitols. Although transfer of galactose residues into raffinose oligosaccharides increased as seeds were maturing, at late stages of seed maturation the accumulation of galactopinitols was preferred to that of RFOs. In the present study, activities of enzymes transferring galactose moieties from galactinol to D-pinitol forming galactopinitol A, and further transfer of galactose moieties from galactinol to mono- and di-galactopinitol A were detected throughout seed development and maturation. This is a new observation, indicating biological potential of winter vetch seeds to synthesize mono-, di- and tri-galactosides of D-pinitol in a pathway similar to RFOs. The pattern of changes in activities of stachyose synthase and enzymes synthesizing galactopinitols (named galactopinitol A synthase and ciceritol synthase) suggests that formation of stachyose, mono- and di-galactopinitol A (ciceritol) is catalyzed by one enzyme. High correlation between activities of verbascose synthase and enzyme catalyzing synthesis of tri-galactopinitol A from galactinol and ciceritol (named tri-galactopinitol A synthase) also suggests that biosynthesis of both types of tri-galactosides was catalyzed by one enzyme, but distinct from stachyose synthase. Changes in concentrations of galactosyl acceptors (sucrose and D-pinitol) can be a factor which regulates splitting of galactose moieties between both types of galactosides in winter vetch seeds.
Acidic glycolipid of ganglio-(containing sialic acid) and sialyl-lactofucosyl-type, SA-Lex (containing sialic acid and fucose) are developmentally regulated and appear to be ubiqitous on neuronal and cancer cell surfaces of animals. Two glycolipid: β-galactosyltransferases, GalT-3 and GalT-4, were characterized in embryonic chicken brain (ECB). Based on substrate competition experiments, these two activities were believed to be due to expression of two gene products. A cDNA fragments (about 600 bp) encoding the catalytic domain of the GalT-4 (UDP-Gal:LcOse3Cer β1,4galactosyltransferase) from ECB and human Colo-205 were isolated. These cDNAs were expressed as a soluble glutathione-S-transferase fusion protein (48 kDa) in Eschericchia coli. Interactions between GlcNAc-, UDP-hexanolamine-, and α-lactalbumin were studied with the purified fusion protein (recombinant and truncated). Functionally it was similar to that of native GalT-4 purified (40000-fold) from 11-day-old ECB. GalT-3 (UDP-Gal:GM2β1,3galactosyltransferase) was purified from 19-day-old ECB, and a polyclonal antibody was produced against the peptide backbone for immunoscreening of a λZAP ECB cDNA expression library. Each of the GalT-3 peptides (62 and 65 kDa was analyzed by protein fingerprinting analysis indicating a similar peptide mapping pattern.
In vitro addition of 16,16'-dimethyl prostaglandin E2 to Golgi-rich membrane fraction in final concentration of 0.1 ng/1 mg of protein increased generally the activity of galactosyltransferase in comparison with control. The percentage of phospholipids in the whole fraction was similar in both investigated groups, only the sum of phosphatidylethanolamine + phosphatide acid was significantly lower after addition of dmPGE2 than in the control (0.001
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