Cytidine-5'-monophospho-N-acetylneuraminic acid galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosyl-glucosylceramide sialyltransferase in the neurohypophysis of the rabbit.
1. Cytidine-5'-monophospho-N-acetylneuraminic acid: (galactosyl-N-acetyl-galactosaminyl-(N-acetylneuraminyl)-galactosyl-glucosylceramide sialyltransferase (CMP-NAcNeu: monosialoganglioside (GM1) sialyltransferase) activity was demonstrated in the neurohypophysis of the rabbit. 2. Optimum activity occurred at pH 6.5 and required the presence of exogenous galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosyl-glucosylceramide (GM1 ganglioside), detergent (Triton X-100), and divalent cation (Mn2+, Mg2+ or Ca2+). 3. The product of the reaction was characterized as N-acetylneuraminyl-galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosyl-glucosylceramide (GD1a) by ascending thin-layer chromatography. 4. Physiological stimulation of vasopressin secretion, by the substitution of 2.2% NaCl for drinking water for 14 days, had no effect on the enzyme activiity or the ganglioside content of the tissue.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D005732:Gangliosides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D010904:Pituitary Gland, Posterior / Q000201:enzymology* / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology; D011817:Rabbits; D012799:Sialyltransferases / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism*
D005732:Gangliosides; D011092:Polyethylene Glycols; D008345:Manganese; D004492:Edetic Acid; D014166:Transferases; D012799:Sialyltransferases; D008274:Magnesium; D002118:Calcium