The reductive pentose phosphate cycle (Benson-Calvin cycle) is the main biochemical pathway for the conversion of atmospheric CO2 to organic compounds. Two unique systems that link light-triggered events in thylakoid membranes with enzyme regulation are located in the soluble portion of chloroplasts (stroma): the ferredoxin-thioredoxin system and ribulose 1,5-bisphosphate carboxylase/oxygenase-Activase (Rubisco-Activase). The ferredoxin-thioredoxin system (ferredoxin, ferredoxin-thioredoxin reductase, and thioredoxin) transforms native (inactive) glyceraldehyde-3-P dehydrogenase, fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase, and phosphoribulokinase to catalytically competent forms. However, the comparison of enzymes reveals the absence of common amino acid sequences for the action of reduced thioredoxin. Thiol/disulfide exchanges appear as the underlying mechanism, but chloroplast metabolites and target domains make the activation process peculiar for each enzyme. On the other hand, Rubisco-Activase facilitates the combination of CO2 with a specific ∈-amino group of ribulose 1,5-bisphosphate carboxylase/oxygenase and the subsequent stabilization of the carbamylated enzyme by Mg2+, in a reaction that depends on ATP and ribulose 1,5-bisphosphate. Most of these studies were carried out in homogenous solutions; nevertheless, a growing body of evidence indicates that several enzymes of the cycle associate either with thylakoid membranes or with other proteins yielding supramolecular complexes in the chloroplast.
Documento: | Artículo |
Título: | The reductive pentose phosphate cycle for photosynthetic CO2 assimilation: Enzyme modulation |
Autor: | Wolosiuk, R.A.; Ballicora, M.A.; Hagelin, K. |
Filiación: | Inst. de Invest. Bioquímicas, Fac. de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina Fundación Campomar, Antonio Machado 151, (1405) Buenos Aires, Argentina |
Palabras clave: | Benson-Calvin cycle; Chloroplasts; Enzyme modulation; Ferredoxin-thioredoxin system; carbon dioxide; ferredoxin; fructose bisphosphatase; glyceraldehyde 3 phosphate dehydrogenase; thioredoxin; transketolase; amino acid sequence; carbon dioxide measurement; chloroplast; enzyme modification; enzyme regulation; pentose phosphate cycle; photosynthesis; plant; priority journal; review; Amino Acid Sequence; Carbon Dioxide; Chloroplasts; Molecular Sequence Data; Pentosephosphate Pathway; Photosynthesis; Support, Non-U.S. Gov't; Thioredoxin |
Año: | 1993 |
Volumen: | 7 |
Número: | 8 |
Página de inicio: | 622 |
Página de fin: | 637 |
Título revista: | FASEB Journal |
Título revista abreviado: | FASEB J. |
ISSN: | 08926638 |
CODEN: | FAJOE |
CAS: | carbon dioxide, 124-38-9, 58561-67-4; ferredoxin, 9040-09-9; fructose bisphosphatase, 9001-52-9; glyceraldehyde 3 phosphate dehydrogenase, 9001-50-7; thioredoxin, 52500-60-4; transketolase, 9014-48-6; Carbon Dioxide, 124-38-9; Thioredoxin, 52500-60-4 |
Registro: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08926638_v7_n8_p622_Wolosiuk |