Isolation and properties of two sialate-O-acetylesterases from horse liver with 4- and 9-O-acetyl specificities

Glycoconj J. 2008 Oct;25(7):625-32. doi: 10.1007/s10719-008-9109-9. Epub 2008 Feb 2.


Sialate-O-acetylesterase was purified almost 900-fold from particle-free supernatants of horse liver by gel filtration, ion-exchange chromatography and isoelectric focussing. The native enzyme on gel filtration exhibits a molecular weight of 54,000 Da. It was separated by isoelectric focussing into two forms with pI values of 4.8 and 5.7, respectively. The esterase with a lower pI hydrolyses only 9-O-acetyl groups from sialic acids (K(M) 1.1 mM), while that with the higher pI esterifies both 4- and 9-O-acetylated monosaccharides at similar rates (K(M) 0.3 M and 1.3 mM, respectively). Both forms are inactive with 7-O-acetylated N-acetylneuraminic acid. Enzyme assays were carried out at the pH optimum (pH 8.4-8.6) using free O-acetylated sialic acids followed by direct analysis of the reaction products by isocratic anion-exchange HPLC. Glycosidically bound sialic acids can also be de-O-acetylated. Horse liver esterase seems to be an essential enzyme for the catabolism of 4-O-acetylated sialoglycoconjugates, since sialidase from this tissue cannot act on 4-O-acetylated sialic acids.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylation
  • Acetylesterase
  • Animals
  • Carboxylic Ester Hydrolases / isolation & purification*
  • Carboxylic Ester Hydrolases / metabolism*
  • Chromatography, Gel
  • Chromatography, High Pressure Liquid
  • Horses*
  • Isoelectric Focusing
  • Liver / enzymology*
  • Molecular Weight
  • Substrate Specificity


  • Carboxylic Ester Hydrolases
  • Acetylesterase
  • sialate O-acetylesterase