A micromethod for measuring carbonic anhydrase activity using 18O exchange between CO2 and H2O. 1988

N Bitterman, and L Lin, and R E Forster
Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia 19104-6085.

We have developed a method of measuring the activity and characteristics of carbonic anhydrase (CA) using the disappearance of 18O from CO2 in 1 ml of gas contained in a glass chamber as it exchanges with H2O in 0.01 ml 0.25 M NaHCO3 solution in a thin (25 micron) porous membrane. Serial gas samples (approximately 0.02 ml) are analyzed in a mass spectrometer to obtain the rate of disappearance of the label. The enzyme activity can be measured inside intact cell or particle membranes. As little as 10(-15) mol of high-activity type CA can be detected at 25 degrees C, and the activity of 200 times this amount can be measured. The uncatalyzed hydration reaction velocity constant was 0.056 +/- 0.004 s-1, in agreement with published data.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008832 Microchemistry The development and use of techniques and equipment to study or perform chemical reactions, with small quantities of materials, frequently less than a milligram or a milliliter.
D008851 Micropore Filters A membrane or barrier with micrometer sized pores used for separation purification processes. Millipore Filters,Filter, Micropore,Filter, Millipore,Filters, Micropore,Filters, Millipore,Micropore Filter,Millipore Filter
D010103 Oxygen Isotopes Stable oxygen atoms that have the same atomic number as the element oxygen, but differ in atomic weight. O-17 and 18 are stable oxygen isotopes. Oxygen Isotope,Isotope, Oxygen,Isotopes, Oxygen
D002245 Carbon Dioxide A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals. Carbonic Anhydride,Anhydride, Carbonic,Dioxide, Carbon
D002256 Carbonic Anhydrases A family of zinc-containing enzymes that catalyze the reversible hydration of carbon dioxide. They play an important role in the transport of CARBON DIOXIDE from the tissues to the LUNG. EC 4.2.1.1. Carbonate Dehydratase,Carbonic Anhydrase,Anhydrases, Carbonic,Dehydratase, Carbonate
D002621 Chemistry A basic science concerned with the composition, structure, and properties of matter; and the reactions that occur between substances and the associated energy exchange.
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863 Hydrogen-Ion Concentration The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D001639 Bicarbonates Inorganic salts that contain the -HCO3 radical. They are an important factor in determining the pH of the blood and the concentration of bicarbonate ions is regulated by the kidney. Levels in the blood are an index of the alkali reserve or buffering capacity. Bicarbonate,Bicarbonate Ions,Hydrogen Carbonates,Bicarbonate Ion,Carbonic Acid Ions,Hydrogen Carbonate,Carbonate, Hydrogen,Carbonates, Hydrogen,Ion, Bicarbonate,Ions, Bicarbonate,Ions, Carbonic Acid

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