Mechanisms for light-dependent regulation of ribulose-1,5-bisphosphate carboxylase activity and photosynthesis in intact leaves
- 1 June 1988
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 85 (11) , 3815-3819
- https://doi.org/10.1073/pnas.85.11.3815
Abstract
The mechanisms involved in the in vivo light-dependent regulation of ribulose-1,5-bisphosphate (Rbu P 2 ) carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] activity in intact leaves were studied. In the three species examined, Phaseolus vulgaris, Beta vulgaris , and Spinacea oleracea , the regulated level of Rbu P 2 carboxylase activity (assayed in vitro with saturating substrate) was highly correlated ( r = 0.96) with the rate of net CO 2 uptake of the corresponding leaves measured over a wide range of photosynthetic photon flux density (PPFD). However, the mechanisms by which the enzyme was regulated differed between these species. In Phaseolus , the inhibitor 2-carboxyarabinitol 1-phosphate (CA P ) accounted for all of the PPFD-dependent regulation of Rbu P 2 carboxylase activity. A similar compound was detected in Beta , and changes in its concentration accounted for about half of the PPFD-dependent regulation of enzyme activity in this species. No CA P was detected in Spinacea , but evidence we obtained suggests that a different inhibitor (possibly Rbu P 2 ) accounts for a significant portion of the PPFD-dependent regulation of enzyme activity in this species. Changes in the activation state of the enzyme were observed with Beta and Spinacea , while in Phaseolus the enzyme was apparently fully activated at all PPFD levels. These results indicate that plant species may differ markedly in the mechanisms they use to regulate Rbu P 2 carboxylase activity as PPFD changes. The results also suggest that tight binding inhibitors are a more widespread mechanism for regulation of this enzyme than previously thought. Furthermore, the results establish the importance of such inhibitors in regulating both the activity of Rbu P 2 carboxylase and whole leaf photosynthesis over a range of PPFD.This publication has 16 references indexed in Scilit:
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