The presence of the two NADP-dependent dehydrogenases of the pentose phosphate pathway has been investigated in plant peroxisomes from pea (Pisum sativum L.) leaves. Both enzymes, glucose-6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44), were present in the matrix of leaf peroxisomes, and their kinetic properties were studied. G6PDH and 6PGDH showed a typical Michaelis-Menten kinetic saturation curve, and had specific activities of 12.4 and 29.6 mU/mg protein, respectively. The Km values of G6PDH and 6PGDH for glucose 6-phosphate and for 6-phosphogluconate were 107.3 and 10.2 μM, respectively. Dithiothreitol did not inhibit G6PDH activity. By isoelectric focusing of peroxisomal matrices, the G6PDH activity was resolved into three isoforms with isoelectric points of 5.55, 5.30 and 4.85. The isoelectric point of peroxisomal 6PGDH was 5.10. Immunoblot analyses of peroxisomal matrix with an antibody against yeast G6PDH revealed a single cross-reactive band of 56 kDa. Post-embedment, EM immunogold labelling of G6PDH confirmed that this enzyme was localized in the peroxisomal matrices, the thylakoid membrane and matrix of chloroplasts, and the cytosol. The presence of the two oxidative enzymes of the pentose phosphate pathway in plant peroxisomes implies that these organelles have the capacity to reduce NADP+ to NADPH for its re-utilization in the peroxisomal metabolism. NADPH is particularly required for the ascorbate-glutathione cycle, which has been recently demonstrated in plant peroxisomes [Jiménez, Hernández, del Río and Sevilla (1997) Plant Physiol. 114, 275-284] and represents an important antioxidant protection system against H2O2 generated in peroxisomes.
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March 1998
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Research Article|
March 01 1998
A dehydrogenase-mediated recycling system of NADPH in plant peroxisomes Available to Purchase
J. Francisco CORPAS;
J. Francisco CORPAS
*Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Apartado 419, E-18080 Granada, Spain
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B. Juan BARROSO;
B. Juan BARROSO
†Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Experimentales, Universidad de Jaén, Paraje ‘Las Lagunillas’ s/n, E-23071 Jaén, Spain
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M. Luisa SANDALIO;
M. Luisa SANDALIO
*Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Apartado 419, E-18080 Granada, Spain
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Stefania DISTEFANO;
Stefania DISTEFANO
*Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Apartado 419, E-18080 Granada, Spain
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M. José PALMA;
M. José PALMA
*Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Apartado 419, E-18080 Granada, Spain
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José A. LUPIÁÑEZ;
José A. LUPIÁÑEZ
‡Departamento de Bioquímica y Biología Molecular, Centro de Ciencias Biológicas, Universidad de Granada, Avenida Fuentenueva s/n, E-18001 Granada, Spain
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A. Luis del RÍO
A. Luis del RÍO
1
*Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Apartado 419, E-18080 Granada, Spain
1To whom correspondence should be addressed.
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Publisher: Portland Press Ltd
Received:
June 06 1997
Revision Received:
October 22 1997
Accepted:
November 03 1997
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1998
1998
Biochem J (1998) 330 (2): 777–784.
Article history
Received:
June 06 1997
Revision Received:
October 22 1997
Accepted:
November 03 1997
Citation
J. Francisco CORPAS, B. Juan BARROSO, M. Luisa SANDALIO, Stefania DISTEFANO, M. José PALMA, José A. LUPIÁÑEZ, A. Luis del RÍO; A dehydrogenase-mediated recycling system of NADPH in plant peroxisomes. Biochem J 1 March 1998; 330 (2): 777–784. doi: https://doi.org/10.1042/bj3300777
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