The modulation of bovine milk D-galactosyltransferase by various phosphatidylethanolamines.
To investigate the possible role of nonbilayer phases in the modulation of glycosyltransferase activity, bovine milk D-galactosyltransferase has been studied in phosphatidylethanolamine (PE) membranes, including soybean PE, egg PE, PE prepared by transphosphatidylation of egg PC, bovine brain PE, plasmalogen PE, and DPPE. The gel-to-liquid crystalline transition (TC) and the lamellar-to-hexagonal transitions (TH) are known for most of the PE compounds. The lower the TC (or TH) value, the greater the stimulation of galactosyltransferase activity in both the lactose- and N-acetyllactosamine-synthetase reactions. No correlation was found between either TC or TH value and the break in the Arrhenius plots for the N-acetyllactosamine synthetase. In membranes consisting of mixtures of PE with PC, the dominant effect was that of PC. The stimulation of activity in the mixed-lipid systems was never greater than that produced by PC alone, therefore the enzyme showed a definite preference for PC in the mixtures.
D000818:Animals; D002417:Cattle; D005260:Female; D005700:Galactosyltransferases / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes; D008892:Milk / Q000201:enzymology*; D010714:Phosphatidylethanolamines / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013816:Thermodynamics
D008081:Liposomes; D010714:Phosphatidylethanolamines; D005700:Galactosyltransferases