Oxygen-18 incorporation into malic acid during nocturnal carbon dioxide fixation in crassulacean acid metabolism plants: a new approach to estimating in vivo carbonic anhydrase activity

Journal Article · Sun Jan 01 04:00:00 EST 1984 · J. Biol. Chem.; (United States)

OSTI ID:6258936

Holtum, J A.M.; Summons, R; Roeske, C A; Comins, H N; O'Leary, M H

Crassulacean acid metabolism (CAM) plants fix carbon dioxide at night by the carboxylation of phosphoenolpyruvate. If CO2 fixation is conducted with TC YO2, then in the absence of carbonic anhydrase, the malate formed by dark CO2 fixation should also contain high levels of carbon-13 and oxygen-18. Conversely, if carbonic anhydrase is present and highly active, oxygen exchange between CO2 and cellular H2O will occur more rapidly than carboxylation, and the ( TC) malate formed will contain little or no oxygen-18 above the natural abundance level. The presence of oxygen-18 in these molecules can be detected either by nuclear magnetic resonance or by mass spectrometry. Studies of phosphoenolpyruvate carboxylase in the presence and absence of carbonic anhydrase in vitro confirm the validity of the method. When CAM plants are studied by this method, we find that most species show incorporation of a significant amount of oxygen-18. Comparison of these results with results of isotope fractionation and gas exchange studies permits calculation of the in vivo activity of carbonic anhydrase toward HCO3 compared with that of phosphoenolpyruvate carboxylase. The ratio (carbonic anhydrase activity/phosphoenolpyruvate carboxylase activity) is species dependent and varies from a low of about 7 for Ananas comosus to values near 20 for Hoya carnosa and Bryophyllum pinnatum, 40 for Kalanchoee daigremontiana, and 100 or greater for Bryophyllum tubiflorum, Kalanchoee serrata, and Kalanchoae tomentosa. Carbonic anhydrase activity increases relative to phosphoenolpyruvate carboxylase activity at higher temperature. 37 references, 2 figures, 8 tables.

• Research Organization: Univ. of Wisconsin, Madison
• DOE Contract Number: AC02-83ER13076
• OSTI ID: 6258936
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 259:11; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
CARBON 13
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON DIOXIDE FIXATION
CARBON ISOTOPES
CARBON OXIDES
CARBON-CARBON LYASES
CARBON-OXYGEN LYASES
CARBONIC ANHYDRASE
CARBOXY-LYASES
CARBOXYLASE
CARBOXYLIC ACIDS
CHALCOGENIDES
DATA
ELECTROMAGNETIC RADIATION
ENZYME ACTIVITY
ENZYMES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
HYDRO-LYASES
HYDROXY ACIDS
IN VIVO
INFORMATION
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LYASES
MAGNETIC RESONANCE
MALIC ACID
MASS SPECTROSCOPY
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PLANTS
RADIATIONS
RESONANCE
SPECTROSCOPY
STABLE ISOTOPES
TRACER TECHNIQUES
VISIBLE RADIATION