Skip to main content
OSTI.GOVU.S. Department of Energy Office of Scientific and Technical Information
U.S. Department of Energy
Office of Scientific and Technical Information
 

Oxygen-18 exchange as a measure of accessibility of CO/sub 2/ and HCO/sub 3//sup -/ to carbonic anhydrase in Chlorella vulgaris (UTEX 263)

Journal Article · · Plant Physiol.; (United States)
OSTI ID:7189666
; ; ;
The exchange of /sup 18/O between CO/sub 2/ and H/sub 2/O in stirred suspensions of Chlorella vulgaris (UTEX 263) was measured using a membrane inlet to a mass spectrometer. The depletion of /sup 18/O from CO/sub 2/ in the fluid outside the cells provides a method to study CO/sub 2/ and HCO/sub 3//sup -/ kinetics in suspensions of algae that contain carbonic anhydrase since /sup 18/O loss to H/sub 2/O is catalyzed inside the cells but not in the external fluid. Low-CO/sub 2/ cells of Chlorella vulgaris (grown with air) were added to a solution containing /sup 18/O enriched CO/sub 2/ and HCO/sub 3//sup -/ with 2 to 15 millimolar total inorganic carbon. The observed depletion of /sup 18/O from CO/sub 2/ was biphasic and the resulting /sup 18/O content of CO/sub 2/ was much less than the /sup 18/O content of HCO/sub 3//sup -/ in the external solution. Analysis of the slopes showed that the Fick's law rate constant for entry of HCO/sub 3//sup -/ into the cell was experimentally indistinguishable from zero (bicarbonate impermeable) with an upper limit of 3 x 10/sup -4/ s/sup -1/ due to experimental errors. The Fick's law rate constant for entry of CO/sub 2/ to the sites of intracellular carbonic anhydrase was large, 0.013 per second, but not as great as calculated for no membrane barrier to CO/sub 2/ flux (6 per second). The experimental value may be explained by a nonhomogeneous distribution of carbonic anhydrase in the cell (such as membrane-bound enzyme) or by a membrane barrier to CO/sub 2/ entry into the cell or both. The CO/sub 2/ hydration activity inside the cells was 160 times the uncatalyzed CO/sub 2/ hydration rate.
Research Organization:
Univ. of Florida, Gainesville
OSTI ID:
7189666
Journal Information:
Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 80:4; ISSN PLPHA
Country of Publication:
United States
Language:
English

Similar Records

Absence of carbonic anhydrase on the surface of red cells suspended in an elutriator
Conference · Fri Feb 28 23:00:00 EST 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) · OSTI ID:5389522
sup 13 C and sup 18 O isotopic disequilibrium in biological carbonates: II. In vitro simulation of kinetic isotope effects
Journal Article · Sat Dec 31 23:00:00 EST 1988 · Geochimica et Cosmochimica Acta; (USA) · OSTI ID:7000662
Use of carbon oxysulfide, a structural analog of CO sub 2 , to study active CO sub 2 transport in the cyanobacterium Synechococcus UTEX 625
Journal Article · Sat Jul 01 00:00:00 EDT 1989 · Plant Physiology; (USA) · OSTI ID:6968377

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALGAE
BIOCHEMICAL REACTION KINETICS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBON-OXYGEN LYASES
CARBONIC ACID
CARBONIC ANHYDRASE
CHALCOGENIDES
CHLORELLA
ENZYME ACTIVITY
ENZYMES
EVEN-EVEN NUCLEI
HYDRO-LYASES
HYDROGEN COMPOUNDS
INORGANIC ACIDS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
LYASES
MICROORGANISMS
NUCLEI
OXIDES
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PLANTS
REACTION KINETICS
STABLE ISOTOPES
TRACER TECHNIQUES
UNICELLULAR ALGAE