Light-Dependent Reduction of Hydrogen Peroxide by Ruptured Pea Chloroplasts 1
AUTOR(ES)
Jablonski, Peter P.
RESUMO
Ruptured pea (Pisum sativum cv. Massey Gem) chloroplasts exhibited ascorbate peroxidase activity as determined by H2O2-dependent oxidation of ascorbate and ascorbate-dependent reduction of H2O2. The ratio of ascorbate peroxidase to NADP-glyceraldehyde 3-phosphate dehydrogenase activity was constant during repeated washing of isolated chloroplasts. This indicates that the ascorbate peroxidase is a chloroplast enzyme. The pH optimum of ascorbate peroxidase activity was 8.2 and the Km value for ascorbate was 0.6 millimolar. Pyrogallol, glutathione, and NAD(P)H did not substitute for ascorbate in the enzyme catalyzed reaction. The enzyme was inhibited by NaN3, KCN, and 8-hydroxyquinoline but not ZnCl2 or iodoacetate. The ascorbate peroxidase activity of sonicated chloroplasts was inhibited by light but not in the presence of substrate concentrations of ascorbate.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=426428Documentos Relacionados
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