Oxygenase and Carboxylase Activities of RuBP Carboxylase from Wheat Leaves

Boyle, Frances A.; Keys, A. J.

doi:10.1007/978-94-017-4973-2_174

Cited by 4 publications

(1 citation statement)

References 7 publications

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“…Fortunately, there is a relationship that is derived from the Michaelis-M enten theory (Laing et al 1974; Jo rd a n & O gren 1981) relating the oxygenase activity to the carboxylase activity. This relation applies apparendy irrespectively of the state of activation of the enzyme or the presence of m any effectors (Boyle & Keys 1984) and is also independent of the concentration of RuBP (Jordan & O gren 1984). It shows th at there is a constant, called the specificity factor ( VCK J V0KC; where Vc and VQ are the K n & xv alues for carboxylation and oxyge and KQ are the Michaelis constants for C 0 2 and 0 2 respectively) which, when multiplied by the ratio of the concentrations of C 0 2 to 0 2 in solution gives the ratio of the rate of carboxylation of RuBP to the rate of its oxygenation.…”

Section: Properties Of R Ubisco Relevant To Rates Of Oxygenation and Photorespirationmentioning

confidence: 99%

Rubisco: its role in photorespiration

Keys

1986

Phil. Trans. R. Soc. Lond. B

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The release of CO 2 during photosynthesis that is due to the production and metabolism of glycollic acid is usually regarded as outward evidence for the wasteful process of photorespiration in plants. In the light, glycollic acid is produced almost entirely as a result of the oxygenase activity of ribulose bisphosphate carboxylaseoxygenase (Rubisco). Metabolism of the glycollic acid not only releases recently assimilated carbon back into the atmosphere but also uses a considerable amount of energy to recycle remaining carbon from the glycollate to intermediates of the photosynthetic carbon reduction cycle. Furthermore, nitrogen from amino acids is released as ammonia during the metabolism of glycollate; some further energy is needed for this ammonia to be reassimilated. The oxygenation of ribulose bisphosphate is competitive with carboxylation and it appears to be the relative concentrations of oxygen and carbon dioxide present in cells containing the enzyme that mainly determine the relative rates of the two reactions in leaves. Systems which concentrate carbon dioxide in photosynthetic cells decrease the extent of photorespiration in C 4 species, certain algae and cyanobacteria. However, carboxylases from different species also vary considerably in their relative capacities to catalyse carboxylation and oxygenation of ribulose bisphosphate under standard conditions. This variation allows some hope that photorespiration might be decreased without recourse to energydependent systems for increasing cellular CO 2 concentrations.

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Section: Properties Of R Ubisco Relevant To Rates Of Oxygenation and Photorespirationmentioning

confidence: 99%