This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (19) Citing Articles via Google Scholar Google Scholar Articles by Anderson, J. W. Articles by House, C. M. Search for Related Content PubMed PubMed Citation Articles by Anderson, J. W. Articles by House, C. M. Agricola Articles by Anderson, J. W. Articles by House, C. M.

Articles

Polarographic Study of Oxaloacetate Reduction by Isolated Pea Chloroplasts

Botany Department, La Trobe University, Bundoora, Victoria 3083, Australia

Suspensions of pea chloroplasts, prepared by differential centrifugation, catalyzed oxaloacetate-dependent O₂ evolution (mean rate of 29 determinations 10.9 micromoles per milligram of chlorophyll per hour, SD 3.2) with the concomitant production of malate. At optimum concentrations of oxaloacetate, both reactions were light-dependent, inhibited by 3-(3,4- dichlorophenyl)-1, 1-dimethylurea and oxalate, and enhanced 2.5- to 4-fold by 10 millimolar NH₄Cl. At concentrations of oxaloacetate (<50 micromolar), 10 millimolar NH₄Cl was inhibitory. The ratio of O₂ evolved to malate produced was 0.39 to 0.58. The ratio of O₂ evolved to oxaloacetate supplied was commensurate with the theoretical value of 0.5.

Chloroplast suspensions contained both NAD- and NADP-malate dehydrogenase activities. It was concluded from oxalate inhibition studies and the promotion of oxaloacetate-dependent O₂ evolution by shocked chloroplasts by NADPH (but not NADH) that the reaction was mediated via the NADP enzyme.