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Calvin cycle inhibitors

The active site of mbisco, the key enzyme involved in photosynthesis, can accept either CO2 or O2. Thus, O2 is a competitive inhibitor of photosynthesis. This process is known as photo-respiration, and involves addition of O2 to ribulose-biphosphate. Products of this reaction enter a metabolic pathway that eventually produces CO2. Unlike cellular respiration, photo-respiration generates no ATP, but it does consume O2. In some plants, as much as 50% of the carbon fixed by the Calvin cycle is respired through photorespiration. Photorespiration is enhanced in hot, dry environments when plant cells close stomata to slow water loss, CO2 is depleted and O2 accumulates. Photorespiration does not occur in prokaryotes, because of the much lower relative concentration of O2 versus CO2 in water compared with air. [Pg.4386]

Thus by means of GA it became possible to show that at the initial steps of the action of the inhibitor the rate of the photosynthetic COg assimilation and formation free isoprene is changed in different ways. These facts show that the mechanism of carbon conversion in Benson-Calvin cycle differs from the one in IE and may be explained by the present scheme. The experimental data of the present paper with numerous references testify that in chloroplasts at least in isoprenereleasing plants beside the ribulosebis-phophat carboxylase/oxygenase another system of carboxylation works the primary product of which is not FGA but acetyl CoA. [Pg.3006]

TCA cycle inhibitor, inhibit photosynthetic CO2 fixation in C thiosulphatum, and (iii) the finding tW C thiosulphalum possesses a-ketoglutarate synthase and pyruvate synthase, enzymes that are peculiar to R.C.C., but lacks ribulose bisphosphate carboxylase and phosphoribulokinase (EC 2.7.1.19), enzymes that are unique to the Calvin cycle. [Pg.600]

Rubisco is inhibited by 2 -carboxy-D-arabinitol-l-phosphate, which accumulates in the chloroplast in the dark [S.Gutteridge etal. (1987) in Progress in Photosynthesis Research (J. Biggins, ed.) Proc. 7th Int. Congr. Photosynth., Vol. 3, pp.395-398] and is rapidly destroyed by light. It has been called fee predawn inhibitor and insures that during the hours of darkness the Calvin cycle is switched off the latter is vital because the Calvin cycle requires ATP and this would have to come from carbohydrate oxidation in the absence of light, a process that would nullify the photosynthesis of previous day. It is believed that 2 -carboxy-D-arabinitol-l-phosphate is inhibitory because its structural similarity to 2-carboxy-3-keto-D-... [Pg.614]

Inhibitors of the Photosynthetic Carbon Reduction (Calvin) Cycle... [Pg.18]


See other pages where Calvin cycle inhibitors is mentioned: [Pg.447]    [Pg.438]    [Pg.309]    [Pg.2910]    [Pg.2928]    [Pg.314]    [Pg.249]    [Pg.638]   
See also in sourсe #XX -- [ Pg.17 , Pg.18 ]




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