D-lactate metabolism in the alga, Chlamydomonas Reinhardtii
(/sup 14/C)D-lactate rapidly accumulates in Chlamydomonas cells under anaerobic conditions from the sugar-phosphate pools which are labeled during photosynthesis with /sup 14/CO/sub 2/. A soluble D-lactate dehydrogenase (30 ..mu..mol NADH oxidized/h/mg Chl), which functions only in the direction of pyruvate reduction, has been partially purified and characterized. The D-lactate is reoxidized in Chlamydomonas by a mitochondrial membrane-bound dehydrogenase. This enzyme is known in the plant literature as glycolate dehydrogenase, an enzyme of the oxidative photosynthetic carbon (C/sub 2/) cycle. This dehydrogenase may be linked to the mitochondrial electron transport chain, although the direct electron acceptor is unknown. Therefore, D-lactate accumulation may be, in part, due to the shut down of electron transport during anaerobiosis. In vivo chase experiments have shown that the D-lactate turns over rapidly when algal cells, which have been grown with air levels of CO/sub 2/ (0.04%), are returned to aerobic conditions in the light. Such turnover is not observed in cells which had been grown with 1 to 5% CO/sub 2/. Cells grown with high CO/sub 2/ have lower levels of glycolate dehydrogenase activity. They are currently using mutants of Chlamydomonas deficient in mitochondrial respiration to study the role of D-lactate oxidation in these algae.
- Research Organization:
- Michigan State Univ., East Lansing
- OSTI ID:
- 7024353
- Report Number(s):
- CONF-8606151-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
550701 -- Microbiology-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALGAE
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBOXYLIC ACID SALTS
CELL CONSTITUENTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHLAMYDOMONAS
ENZYME ACTIVITY
ENZYMES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LACTATES
METABOLISM
MICROORGANISMS
MITOCHONDRIA
ORGANOIDS
OXIDES
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PLANTS
SYNTHESIS
TRACER TECHNIQUES
UNICELLULAR ALGAE