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

Journal Article · Fri Jan 01 04:00:00 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), Journal Name: Plant Physiol.; (United States) Vol. 86:1; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

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