Glycolipid biosynthesis in rainbow trout: characterization of a beta 1----4galactosyltransferase independent from regulation by alpha-lactalbumin.
1. Rainbow trout (Salmo gairdneri) beta 1----4galactosyltransferase has been characterized and its properties compared to the mammalian enzyme. 2. Transfer of galactose to lactotriaosylceramide (Lc3) was optimal in the presence of 0.12% Triton CF-54 and Mn2+, in a pH range of 6.5-7.5. 3. Apparent Km values for donor UDPgalactose and acceptor Lc3 were determined to be 40 and 38 microM, respectively. 4. Glycolipid substrate specificity was found with only Lc3 being an efficient acceptor. Transfer of galactose to glycosylceramide, efficient with mammalian enzyme, was 42-fold slower. 5. In contrast to mammalian enzyme, rainbow trout beta 1----4galactosyltransferase was found to be independent from regulation by alpha-lactalbumin by the inability of alpha-lactalbumin-Sepharose to bind the enzyme and by failure of alpha-lactalbumin to inhibit the enzyme activity.
Jenner
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NK
Pacific Northwest Research Foundation, Seattle, WA 98122.
Holmes
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EH
D000818:Animals; D002240:Carbohydrate Sequence; D003902:Detergents / Q000494:pharmacology; D005690:Galactose / Q000378:metabolism; D005700:Galactosyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006017:Glycolipids / Q000096:biosynthesis*; D006056:Golgi Apparatus / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007768:Lactalbumin / Q000378:metabolism / Q000494:pharmacology*; D007790:Lactosylceramides / Q000378:metabolism; D008099:Liver / Q000201:enzymology; D008345:Manganese / Q000494:pharmacology; D008969:Molecular Sequence Data; D013379:Substrate Specificity; D014337:Trout / Q000378:metabolism*; D014531:Uridine Diphosphate Galactose / Q000378:metabolism
D003902:Detergents; D006017:Glycolipids; D007790:Lactosylceramides; D014531:Uridine Diphosphate Galactose; D008345:Manganese; C025575:lactotriaosylceramide; D007768:Lactalbumin; D005700:Galactosyltransferases; D005690:Galactose