Glucose respiration in the intact chloroplast of Chlamydomonas reinhardtii
- Brandeis Univ., Waltham, MA (United States)
Chloroplastic respiration was monitored by measuring {sup 14}CO{sub 2} from {sup 14}C glucose in the darkened Chlamydomonas reinhardtii F-60 chloroplast, The patterns of {sup 14}CO{sub 2} evolution from labeled glucose in the absence and presence of the inhibitors iodoacetamide, glycolate-2-phosphate, and phosphoenolypyruvate were those expected from the oxidative pentose phosphate cycle and glycolysis. The K{sub m} for glucose was 56 micromolar and for MgATP was 200 micromolar. Release of {sup 14}CO{sub 2} was inhibited by phloretin and inorganic phosphate. Comparing the inhibition of CO{sub 2} evolution generated by pH 7.5 with respect to pH 8.2 (optimum) in chloroplasts given C-1, C-2, and C-6 labeled glucose indicated that a suboptimum pH affects the recycling of the pentose phosphate intermediates to a greater extent than CO{sub 2} evolution from C-1 of glucose. Respiratory inhibition by pH 7.5 in the darkened chloroplast was alleviated by NH{sub 4}Cl and KCl (stromal alkalating agents), iodoacetamide (an inhibitor of glyceraldehyde 3-phosphate dehydrogenase), or phosphoenolypyruvate (an inhibitor of phosphofructokinase). It is concluded that the site which primarily mediates respiration in the darkened Chlamydomonas chloroplast is the fructose-1,6-bisphosphatase/phosphofructokinase junction. The respiratory pathways described here can account for the total oxidation of a hexose to Co{sub 2} and for interactions between carbohydrate metabolism and the oxyhydrogen reaction in algal cells adapted to a hydrogen metabolism.
- DOE Contract Number:
- FG02-86ER13486
- OSTI ID:
- 5742027
- Journal Information:
- Plant Physiology; (United States), Vol. 95:1; ISSN 0032-0889
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHLAMYDOMONAS
PHYSIOLOGY
CHLOROPLASTS
RESPIRATION
BIOLOGICAL PATHWAYS
CARBON 14 COMPOUNDS
CARBON DIOXIDE
GLUCOSE
INHIBITION
METABOLISM
PH VALUE
TRACER TECHNIQUES
ALDEHYDES
ALGAE
CARBOHYDRATES
CARBON COMPOUNDS
CARBON OXIDES
CELL CONSTITUENTS
CHALCOGENIDES
CHLOROPHYCOTA
HEXOSES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MICROORGANISMS
MONOSACCHARIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLANTS
SACCHARIDES
UNICELLULAR ALGAE
551001* - Physiological Systems- Tracer Techniques