title: Multiple forms of sheep serum A-esterase activity associated with the high-density lipoprotein.
abstract: Five lipoproteins of sheep serum expressing A-esterase activity, but with differing activities towards four organophosphate substrates, were separated by a combination of gel filtration and ion-exchange chromatography. Each had an Mr of approx. 360,000 and contained a major peptide of Mr 28,000-30,000 that appeared to be present as several isoforms on urea/agarose isoelectric focusing. In every case this peptide split into a number of bands on urea/agarose isoelectric focusing. The bands appear to represent isoforms of the peptide, and four lipoproteins yielded characteristic patterns of bands. This peptide resembles the apolipoprotein A-I of human serum, and available evidence suggests that this is the protein that expresses A-esterase activity. Evidence is presented for the existence of different species of high-density lipoprotein HDL2 particles containing different complements of peptide isoforms and expressing contrasting substrate specificities towards organophosphates.
mesh_terms: D000818:Animals; D043303:Aryldialkylphosphatase; D004390:Chlorpyrifos / Q000031:analogs & derivatives / Q000378:metabolism; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003372:Coumaphos / Q000031:analogs & derivatives / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007526:Isoelectric Point; D007527:Isoenzymes / Q000097:blood* / Q000302:isolation & purification; D008075:Lipoproteins, HDL / Q000097:blood*; D009943:Organophosphorus Compounds / Q000378:metabolism; D010261:Paraoxon / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000097:blood* / Q000302:isolation & purification; D012756:Sheep
chemical_list: D007527:Isoenzymes; D008075:Lipoproteins, HDL; D009943:Organophosphorus Compounds; C009618:O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphate; C000912:diazoxon; D010744:Phosphoric Monoester Hydrolases; D043303:Aryldialkylphosphatase; C007130:coroxon; D004390:Chlorpyrifos; D003372:Coumaphos; D010261:Paraoxon