Plant Physiol. Illumina
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Plant Physiology 71:772-776 (1983)
© 1983 American Society of Plant Biologists

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Articles

Mechanism of Glyoxylate Decarboxylation in the Glycolate Pathway in Euglena gracilis Z 1

Participation of Mn2+-Dependent NADPH Oxidase in Chloroplasts

Akiho Yokota, Akiko Kawabata and Shozaburo Kitaoka

Department of Agricultural Chemistry, University of Osaka Prefecture, Sakai, Osaka 591, Department of Natural Science, Osaka Women's University, Sakai, Osaka 590, Japan

The mechanism for decarboxylating the carboxyl carbon of glycolate was studied in Euglena gracilis Z, which liberates more than 70% of the carboxyl carbon as CO2 during glycolate metabolism.

In the isolated mitochondria of E. gracilis, glycolate was oxidized to glyoxylate, 25% of which was aminated to glycine, with the remaining unchanged in the presence of glutamate; in the absence of the amino donor, glyoxylate was not changed. Irrespective of the presence or absence of the amino donor, no decarboxylation took place in Euglena mitochondria. In Euglena chloroplasts glyoxylate was actively decarboxylated by the action of hydrogen peroxide generated by the reaction of a Mn2+-dependent NADPH oxidase. This enzyme was purified 120-fold over the crude extract and some of its properties studied. Oxidation of one molecule of NADPH was accompanied by the formation of one molecule of H2O2; the NADPH oxidation was not attributable to the action of L-ascorbate peroxidase, the sole peroxidase present in E. gracilis. Specific participation of chloroplasts and mitochondria in glycolate metabolism is discussed.

1 Supported partially by Japan Securities Scholarship Foundation. This paper is the seventh in a series on the metabolism of glycolate in Euglena gracilis.






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Copyright © 1983 by the American Society of Plant Biologists