title: The number of acetylcholinesterase molecules in the rat megakaryocyte.
abstract: A megakaryocyte cell series from rat bone marrow has been examined by the isotopic di-isopropyl fluorophosphate (DFP) method for esterases. After complete reaction with 32P-DFP, the numbers of DFP-reacted molecules inindividual cells havebeen determined by beta trackauto-radiography. Previous work has shown the percentage of organophosphate-sensitive sites in these cells which can be taken as active centers of acetylcholinesterase (AChase). Combining these data, the absolute numbers of organophosphate-sensitive esterase molecules and AChase molecules per cell were determined. Histograms show a narrow spread of values within each of four size classes from megakaryoblast to fully mature megakaryocyte, but, with means increasing 4-fold through this series, approximately in proportion to cell volume. A rat megakaryoblast has 2 X 10(6) AChase molecules, and a megakaryocyte (of 48-micro diameter) has 7.6 X 10(6) molecules. The apparent turnover number of the enzyme for intracellular reaction with substrate is calculated and compared with turnover numbers available for other AChases.
authors.affiliation: Molecular Enzymology Unit, Department of Biochemistry, School of Medicine, State University of New York, Buffalo, New York 14214, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Darzynkiewicz
authors.forename: A W
authors.initials: AW
authors.lastname: Rogers
authors.forename: E A
authors.initials: EA
authors.lastname: Barnard
mesh_terms: D000110:Acetylcholinesterase / Q000032:analysis / Q000737:chemistry*; D000818:Animals; D001345:Autoradiography / Q000379:methods; D007531:Isoflurophate / Q000737:chemistry; D008297:Male; D008533:Megakaryocytes / Q000201:enzymology* / Q000648:ultrastructure; D010761:Phosphorus Radioisotopes / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D012680:Sensitivity and Specificity
chemical_list: D010761:Phosphorus Radioisotopes; D007531:Isoflurophate; D000110:Acetylcholinesterase