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 HighWire Citing Articles via CrossRef Citing Articles via Web of Science (19) Citing Articles via Google Scholar Google Scholar Articles by Kleczkowski, L. A. Articles by Givan, C. V. Search for Related Content PubMed PubMed Citation Articles by Kleczkowski, L. A. Articles by Givan, C. V. Agricola Articles by Kleczkowski, L. A. Articles by Givan, C. V.

Metabolism and Enzymology

Enzymology of the Reduction of Hydroxypyruvate and Glyoxylate in a Mutant of Barley Lacking Peroxisomal Hydroxypyruvate Reductase ¹

Department of Botany, Washington State University, Pullman, Washington 99164-4238, Institute of Environmental and Biological Sciences, University of Lancaster LA1 4YQ, United Kingdom, Department of Biology, University of Newcastle upon Tyne NE1 7RU, United Kingdom

The use of LaPr 88/29 mutant of barley (Hordeum vulgare), which lacks NADH-preferring hydroxypyruvate reductase (HPR-1), allowed for an unequivocal demonstration of at least two related NADPH-preferring reductases in this species: HPR-2, reactive with both hydroxypyruvate and glyoxylate, and the glyoxylate specific reductase (GR-1). Antibodies against spinach HPR-1 recognized barley HPR-1 and partially reacted with barley HPR-2, but not GR-1, as demonstrated by Western immunoblotting and immunoprecipitation of proteins from crude leaf extracts. The mutant was deficient in HPR-1 protein. In partially purified preparations, the activities of HPR-1, HPR-2, and GR-1 could be differentiated by substrate kinetics and/or inhibition studies. Apparent K_m values of HPR-2 for hydroxypyruvate and glyoxylate were 0.7 and 1.1 millimolar, respectively, while the K_m of GR-1 for glyoxylate was 0.07 millimolar. The K_m values of HPR-1, measured in wild type, for hydroxypyruvate and glyoxylate were 0.12 and 20 millimolar, respectively. Tartronate and P-hydroxypyruvate acted as selective uncompetitive inhibitors of HPR-2 (K_i values of 0.3 and 0.4 millimolar, respectively), while acetohydroxamate selectively inhibited GR-1 activity. Nonspecific contributions of HPR-1 reactions in assays of HPR-2 and GR-1 activities were quantified by a direct comparison of rates in preparations from wild-type and LaPr 88/29 plants. The data are evaluated with respect to previous reports on plant HPR and GR activities and with respect to optimal assay procedures for individual HPR-1, HPR-2, and GR-1 rates in leaf preparations.

¹ Supported in part by the National Science Foundation grant DCB-8816322 (to G.E.E.) and by grants AG 89/13 and PG 89/502 (to P.J.L. and R.D.B.).

This article has been cited by other articles:

				H. Xu, J. Zhang, J. Zeng, L. Jiang, E. Liu, C. Peng, Z. He, and X. Peng Inducible antisense suppression of glycolate oxidase reveals its strong regulation over photosynthesis in rice J. Exp. Bot., April 1, 2009; 60(6): 1799 - 1809. [Abstract] [Full Text] [PDF]

				A. Wingler, A. von Schaewen, R. C. Leegood, P. J. Lea, and W. Paul Quick Regulation of Leaf Senescence by Cytokinin, Sugars, and Light . Effects on NADH-Dependent Hydroxypyruvate Reductase Plant Physiology, January 1, 1998; 116(1): 329 - 335. [Abstract] [Full Text]