title: Carbonic anhydrase activity of intact carbonic anhydrase II-deficient human erythrocytes.
abstract: Intact erythrocytes from subjects with deficiency of blood carbonic anhydrase (CA) II and from normal subjects were assayed for enzyme activity by use of an 18O exchange technique in a solution containing 25 mM (CO2 + NaHCO3) plus 125 mM NaCl. At 25 degrees C and pH 7.4, the catalyzed reaction velocity was 0.32 +/- 0.04 M/s for the CA II-deficient and 1.60 +/- 0.12 M/s for the normal cells, a ratio of 1:5. Under the same conditions at 37 degrees C the relative difference between the CA II-deficient and normal cells was much less: the velocity for the CA II-deficient cells was 0.84 +/- 0.07 M/s and for the normal cells 1.60 +/- 0.32 M/s, a ratio of 1:1.9. Results were comparable for the hemolysates with the NaHCO3 reduced to 85 mM (the corresponding intracellular concentration): at 25 degrees C CA II-deficient cells had a velocity of 0.36 +/- 0.01 M/s compared with 1.12 +/- 0.04 M/s for the normal cells, a ratio of 1:3.1. At 37 degrees C again the relative difference between hemolysates from CA II normal and deficient cells was much less: the CA II-deficient cells had a reaction velocity of 1.17 +/- 0.22 M/s vs. 2.60 +/- 0.36 M/s for the normal cells, a ratio of 1:2.2. The greater fractional reduction of enzyme velocity of CA II-deficient cells at 25 degrees C compared with 37 degrees C appears to be explained by a greater chloride inhibition of the presumed CA I at the lower temperature.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia 19104-6085.
authors.forename: S J
authors.initials: SJ
authors.lastname: Dodgson
authors.forename: R E
authors.initials: RE
authors.lastname: Forster
authors.forename: W S
authors.initials: WS
authors.lastname: Sly
authors.forename: R E
authors.initials: RE
authors.lastname: Tashian
mesh_terms: D000328:Adult; D001639:Bicarbonates; D002245:Carbon Dioxide / Q000494:pharmacology; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology; D002256:Carbonic Anhydrases / Q000097:blood / Q000172:deficiency*; D002712:Chlorides / Q000494:pharmacology; D004912:Erythrocytes / Q000201:enzymology*; D005016:Ethoxzolamide / Q000494:pharmacology; D005260:Female; D006579:Heterozygote; D006801:Humans; D008297:Male; D010103:Oxygen Isotopes; D012964:Sodium; D017693:Sodium Bicarbonate; D012996:Solutions
chemical_list: D001639:Bicarbonates; D002257:Carbonic Anhydrase Inhibitors; D002712:Chlorides; D010103:Oxygen Isotopes; D012996:Solutions; D002245:Carbon Dioxide; D017693:Sodium Bicarbonate; D012964:Sodium; D002256:Carbonic Anhydrases; D005016:Ethoxzolamide