Kinetic studies on the acid hydrolysis of the methyl ketoside of unsubstituted and O-acetylated N-acetylneuraminic acid.
The hydrolysis of the model compound 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl-alpha-d-neuraminic acid and neuraminidase (Vibrio cholerae) closely resembled that of the O-acetylated sialic acid residues of rabbit Tamm-Horsfall glycoprotein. This confirmed that O-acetylation was responsible for the unusually slow rate of acid hydrolysis of O-acetylated sialic acid residues observed in rabbit Tamm-Horsfall glycoprotein and their resistance to hydrolysis by neuraminidase. The first-order rate constant of hydrolysis of 2-methyl-N-acetyl-alpha-d-neuraminic acid by 0.05m-H(2)SO(4) was 56-fold greater than that of 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl -alpha-d-neuraminic acid. Kinetic studies have shown that in the pH range 1.00-3.30, the observed rate of hydrolysis of 2-methyl-N-acetyl-alpha-d-neuraminic acid can be attributed to acid-catalysed hydrolysis of the negatively charged CO(2) (-) form of the methyl ketoside.
D000085:Acetates; D000215:Acylation; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008759:Methylglycosides; D009438:Neuraminic Acids; D009439:Neuraminidase; D013464:Sulfuric Acids; D014734:Vibrio cholerae / Q000201:enzymology
D000085:Acetates; D008759:Methylglycosides; D009438:Neuraminic Acids; D013464:Sulfuric Acids; D009439:Neuraminidase