Enzymatic 4-O-acetylation of N-acetylneuraminic acid in guinea-pig liver

Sialic acids from the liver and serum of guinea-pig are composed of N-acetylneuraminic acid (Neu5Ac; 85% and 61%, respectively), N-acetyl-4-O-acetylneuraminic acid (Neu4,5Ac2; 10% and 32%, respectively) and N-glycolylneuraminic acid (Neu5Gc; 5% and 7%, respectively), besides traces of N-glycolyl-4-O...

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Bibliographic Details
Published in:Glycoconjugate journal 1998-09, Vol.15 (9), p.895-904
Main Authors: Iwersen, M, Vandamme-Feldhaus, V, Schauer, R
Format: Article
Language:English
Subjects:
Acetylation
Acetyltransferases - metabolism
Acids
Animals
Chromatography
Coenzyme A - pharmacology
Female
Golgi Apparatus - enzymology
Guinea Pigs
Hydrogen-Ion Concentration
Kinetics
Liver - enzymology
Male
Mass spectrometry
N-Acetylneuraminic Acid - metabolism
Neuraminic Acids - metabolism
Sialic Acids - analysis
Sialic Acids - metabolism
Substrate Specificity
Temperature
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Summary:Sialic acids from the liver and serum of guinea-pig are composed of N-acetylneuraminic acid (Neu5Ac; 85% and 61%, respectively), N-acetyl-4-O-acetylneuraminic acid (Neu4,5Ac2; 10% and 32%, respectively) and N-glycolylneuraminic acid (Neu5Gc; 5% and 7%, respectively), besides traces of N-glycolyl-4-O-acetylneuraminic acid in serum. The analysis was carried out using thin-layer chromatography, high-performance liquid chromatography, electron impact ionization mass spectrometry, and different enzymes (sialidase, sialate esterase, and sialate-pyruvate lyase after hydrolysis and purification of the sialic acids by ion-exchange chromatography). We showed that this O-acetylation of sialic acids is due to the activity of an acetyl-coenzyme A:sialate-4-O-acetyltransferase (EC 2.3.1.44), which occurs together with sialyltransferase activity in Golgi-enriched membrane fractions of guinea-pig liver. The enzyme operates optimally at 30 degrees C in 70 mM potassium phosphate buffer at pH 6.7 and in the presence of 90 mM KCI with an apparent KM for AcCoA of 0.6 1microM and a Vmax of 20 pmol/mg protein x min. The enzyme is inhibited by coenzyme A in a mixed-competitive manner (Ki = 4.2 microM), as well as by parachloromercuribenzoate, MnCl2, saponin and Triton X-100.
ISSN:0282-0080
1573-4986
DOI:10.1023/a:1006911100081