In vitro biosynthesis of the tetrasialoganglioside GQ1b

• Published in: The Journal of biological chemistry Vol. 257; no. 1; pp. 249 - 252
• Main Authors: YOHE, H. C, MACALA, L. J, YU, R. K
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 10-01-1982
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Brain - enzymology; Cations, Divalent; Cell Membrane - enzymology; Chick Embryo; Detergents - pharmacology; Fundamental and applied biological sciences. Psychology; Gangliosides - biosynthesis; Hydrogen-Ion Concentration; Kinetics; Lipids; Neuraminic Acids - metabolism; Other biological molecules; Sialyltransferases - metabolism; Subcellular Fractions - enzymology; Transferases - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)68353-5

A sialyltransferase activity which catalyzes the synthesis of the tetrasialoganglioside GQ1b (N-acetylneuraminyl-N-acetylneuraminylgalactosyl-N-acetylgalactosaminyl
[N-acetylneuraminyl-N-acetylneuraminyl]-galactosylglucosylceramide) from added trisialoganglioside GT1b (N-=acetylneuraminylgalactosyl-N-acetylgalactosaminyl
[N-acetylneuraminyl-N-acetylneuraminyl]galactosylglucosylceramide) and CMP-N-acetyl[4-14C]neuraminic acid has been demonstrated
using a membrane fraction of embryonic chick brain. Optimum enzymatic activity was obtained using the detergent Triton CF-54
at a pH of 6.6. Enzyme activity appeared unaffected by Ca2+, Mg2+, Mn2+, EDTA, or histone. A slight elevation in activity
was seen in the presence of Hg2+. When the disialoganglioside GD1b (galactosyl-N-acetylgalactosaminyl [N-acetylneuraminyl-N-acetylneuraminyl]galactosylglucosylceramide)
was used as the glycolipid substrate, approximately 15% of the radioactive label was found in GQ1b. When this GQ1b was subjected
to a periodate oxidation-borohydride reduction, the distribution of radioactive label was consistent with GQ1b being the major
tetrasialoganglioside product and that its synthesis could proceed via the sequence GD1b-GT1b-GQ1b.