Choline oxidation by intact spinach chloroplasts. [Spinacia oleracea L]

Journal Article · Fri Jan 01 00:00:00 EST 1988 · Plant Physiol.; (United States)

OSTI ID:6998543

Weigel, P; Lerma, C; Hanson, A D

Plants synthesize betaine by a two-step oxidation of choline (choline ..-->.. betaine aldehyde ..-->.. betaine). Protoplast-derived chloroplasts of spinach (Spinacia oleracea L.) carry out both reactions, more rapidly in light than in darkness. We investigated the light-stimulated oxidation of choline, using spinach chloroplasts isolated directly from leaves. The rates of choline oxidation obtained (dark and light rates: 10-50 and 100-300 nanomoles per hour per milligram chlorophyll, respectively) were approximately 20-fold higher than for protoplast-derived chloroplasts. Betaine aldehyde was the main product. Choline oxidation in darkness and light was suppressed by hypoxia. Neither uncouplers not the Calvin cycle inhibitor glyceraldehyde greatly affected choline oxidation in the light, and maximal choline oxidation was attained far below light saturation of CO/sub 2/ fixation. The light stimulation of choline oxidation was abolished by the PSII inhibitors DCMU and dibromothymoquinone, and was partially restored by adding reduced diaminodurene, an electron donor to PSI. Both methyl viologen and phenazine methosulfate prevented choline oxidation. Adding dihydroxyacetone phosphate, which can generate NADPH in organello, doubled the dark rate of choline oxidation. These results indicate that choline oxidation in chloroplasts requires oxygen, and reducing power generated from PSI. Enzymic reactions consistent with these requirements are discussed.

• Research Organization: Michigan State Univ., East Lansing (USA)
• DOE Contract Number: AC02-76ER01338
• OSTI ID: 6998543
• Journal Information: Plant Physiol.; (United States), Vol. 86:1
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CHLOROPLASTS
BIOCHEMICAL REACTION KINETICS
CHOLINE
OXIDATION
ALDEHYDES
ANOXIA
BETAINE
BIPYRIDINES
CALVIN CYCLE SPECIES
CHLOROPHYLL
ENZYME ACTIVITY
INHIBITION
NADP
PHENAZINE
PHOTOSYNTHESIS
PLANT CELLS
QUINONES
RESPONSE MODIFYING FACTORS
SPINACH
VISIBLE RADIATION
ALCOHOLS
AMINES
AMINO ACIDS
AMMONIUM COMPOUNDS
AROMATICS
AZINES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
COENZYMES
DRUGS
ELECTROMAGNETIC RADIATION
FOOD
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
KINETICS
LIPOTROPIC FACTORS
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHYTOCHROMES
PIGMENTS
PLANTS
PORPHYRINS
PROTEINS
PYRAZINES
PYRIDINES
QUATERNARY COMPOUNDS
RADIATIONS
REACTION KINETICS
SYNTHESIS
VEGETABLES
550200* - Biochemistry