ROLE OF OLIGOSACCHARIDES IN THE PHARMACOKINETICS OF TISSUE-DERIVED AND GENETICALLY-ENGINEERED CHOLINESTERASES

To understand the role of glycosylation in the circulation of cholines terases, we compared the mean residence time of five tissue-derived an d two recombinant cholinesterases (injected intravenously in mice) wit h their oligosaccharide profiles. Monosaccharide composition analysis revealed differences in the total carbohydrate, galactose, and sialic acid contents. The molar ratio of sialic acid to galactose residues on tetrameric human serum butyrylcholinesterase, recombinant human butyr ylcholinesterase, and recombinant mouse acetylcholinesterase was found to be similar to 1.0. For Torpedo californica acetylcholinesterase, m onomeric and tetrameric fetal bovine serum acetylcholinesterase, and e quine serum butyrylcholinesterase, this ratio was similar to 0.5. Howe ver, the circulatory stability of cholinesterases could not be correla ted with the sialic acid-to-galactose ratio. Fractionation of the tota l pool of oligosaccharides obtained after neuraminidase digestion reve aled one major oligosaccharide for human serum butyrylcholinesterase a nd three or four major oligosaccharides in other cholinesterases. The glycans of tetrameric forms of plasma cholinesterases (human serum but yrylcholinesterase, fetal bovine serum acetylcholinesterase, and equin e serum butyrylcholinesterase) clearly demonstrated a reduced heteroge neity and higher maturity compared with glycans of monomeric fetal bov ine serum acetylcholinesterase, dimeric tissue-derived T. californica acetylcholinesterase, and recombinant cholinesterases. T. californica acetylcholinesterase, recombinant cholinesterases, and monomeric fetal bovine serum acetylcholinesterase showed a distinctive shorter mean r esidence time (44-304 min) compared with tetrameric forms of plasma ch olinesterases (1902-3206 min). Differences in the pharmacokinetic para meters of cholinesterases seem to be due to the combined effect of the molecular weight and charge-and size-based heterogeneity in glycans.