The role of CMP-N-acetylneuraminic acid hydroxylase in determining the level of N-glycolylneuraminic acid in porcine tissues.
The biosynthesis of the sialic acid N-glycolylneuraminic acid (Neu5Gc) occurs by the action of cytidine monophosphate-N-acetylneuraminate (CMP-Neu5Ac) hydroxylase. Previous investigations on a limited number of tissues suggest that the activity of this enzyme governs the extent of glycoconjugate sialylation with Neu5Gc. Using improved analytical procedures and a panel of nine porcine tissues, each expressing different amounts of Neu5Gc, we have readdressed the issue of the regulation of Neu5Gc incorporation into glycoconjugates. The following parameters were measured for each tissue: the molar ratio Neu5Gc/Neu5Ac, the activity of the hydroxylase, and the relative amount of hydroxylase protein, as determined by enzyme-linked immunosorbent assay (ELISA). A positive correlation between the activity of the hydroxylase and the molar ratio Neu5Gc/Neu5Ac was observed for each tissue. In addition, the hydroxylase activity correlated with the amount of enzyme protein, though in heart and lung disproportionately large amounts of immunoreactive protein were detected. Taken together, the results suggest that the incorporation of Neu5Gc into glycoconjugates is generally controlled by the amount of hydroxylase protein expressed in a tissue.
Biochemisches Institut, Christian-Albrechts-Universität zu Kiel, Germany.
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Malykh
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L
Shaw
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Schauer
D000818:Animals; D004791:Enzyme Inhibitors; D004797:Enzyme-Linked Immunosorbent Assay; D006001:Glycoconjugates / Q000096:biosynthesis; D006899:Mixed Function Oxygenases / Q000737:chemistry*; D019158:N-Acetylneuraminic Acid / Q000032:analysis; D009438:Neuraminic Acids / Q000032:analysis*; D013552:Swine
D004791:Enzyme Inhibitors; D006001:Glycoconjugates; D009438:Neuraminic Acids; C032592:N-glycolylneuraminic acid; D006899:Mixed Function Oxygenases; C074383:CMPacetylneuraminate monooxygenase; D019158:N-Acetylneuraminic Acid