0000000000444248
AUTHOR
Hemanth P. K. Sudhani
Reversible inhibition of CO2fixation by ribulose 1,5-bisphosphate carboxylase/oxygenase through the synergic effect of arsenite and a monothiol
The activity of the photosynthetic carbon-fixing enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), is partially inhibited by arsenite in the millimolar concentration range. However, micromolar arsenite can fully inhibit Rubisco in the presence of a potentiating monothiol such as cysteine, cysteamine, 2-mercaptoethanol or N-acetylcysteine, but not glutathione. Arsenite reacts specifically with the vicinal Cys172-Cys192 from the large subunit of Rubisco and with the monothiol to establish a ternary complex, which is suggested to be a trithioarsenical. The stability of the complex is strongly dependent on the nature of the monothiol. Enzyme activity is fully recovered through …
Control of the activity of Rubisco from Chlamydomonas reinhardtii through the redox state of its cysteine residues
RESUMEN de la MEMORIA de TESIS DOCTORAL titulada: CONTROL OF THE ACTIVITY OF RUBISCO FROM CHLAMYDOMONAS REINHARDTII THROUGH THE REDOX STATE OF ITS CYSTEINE RESIDUES. presentada por HEMANTH PHANI KUMAR SUDHANI para optar al título de DOCTOR dentro del Programa Oficial de Posgrado en BIOTECNOLOGÍA (D030-01) de la Universitat de València. Tema: La actividad del enzima fijador de carbono en eucariotas fotosintéticos, la ribulosa 1,5-bisfosfato carboxilas/oxigenasa (Rubisco), puede regularse in vitro por efectores redox. Esta capacidad existe en los enzimas de todas las especies eucarióticas ensayadas y se supone que reside en un número relativamente reducido de residuos de cisteína conservados,…
Control of the ribulose 1,5-bisphosphate carboxylase/oxygenase activity by the chloroplastic glutathione pool.
The CO2-fixing activity of ribulose 1,5-bisphosphate carboxylase/oxygenase depends on the redox state of its cysteines. Disulfides like cystamine or 5,5'-dithio-bis(2-nitrobenzoic acid), but not oxidized glutathione, switch the enzyme to the inactive oxidized form. Conversely, thiols like cysteamine, cysteine, dithiotreitol or 2-mercaptoethanol, but not reduced glutathione, recover enzymatic activity after a previous oxidation. Direct regulation of the carboxylase activity by the chloroplastic glutathione pool is hindered by kinetic barriers impeding access to the critical residues. However, reduced glutathione can drive the recovery of activity by means of minute amounts of smaller interme…