Plant Physiol. Drug Metab Dispos
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Plant Physiology 69:1136-1139 (1982)
© 1982 American Society of Plant Biologists

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Articles

Effects of Glycine Hydroxamate, Carbon Dioxide, and Oxygen on Photorespiratory Carbon and Nitrogen Metabolism in Spinach Mesophyll Cells 1

Arthur L. Lawyer2, Karen L. Cornwell, Sherry L. Gee and James A. Bassham

Laboratory of Chemical Biodynamics, University of California, Berkeley, California 94720, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720

The effects of added glycine hydroxamate on the photosynthetic incorporation of 14CO2 into metabolites by isolated mesophyll cells of spinach (Spinacia oleracea L.) was investigated under conditions favorable to photorespiratory (PR) metabolism (0.04% CO2 and 20% O2) and under conditions leading to nonphotorespiratory (NPR) metabolism (0.2% CO2 and 2.7% O2). Glycine hydroxamate (GH) is a competitive inhibitor of the photorespiratory conversion of glycine to serine, CO2 and NH4+. During PR fixation, addition of the inhibitor increased glycine and decreased glutamine labeling. In contrast, labeling of glycine decreased under NPR conditions. This suggests that when the rate of glycolate synthesis is slow, the primary route of glycine synthesis is through serine rather than from glycolate. GH addition increased serine labeling under PR conditions but not under NPR conditions. This increase in serine labeling at a time when glycine to serine conversion is partially blocked by the inhibitor may be due to serine accumulation via the "reverse" flow of photorespiration from 3-P-glycerate to hydroxypyruvate when glycine levels are high. GH increased glyoxylate and decreased glycolate labeling. These observations are discussed with respect to possible glyoxylate feedback inhibition of photorespiration.

2 Present address: Chevron Chemical Company, 940 Hensley Street, Richmond, CA 94804.

1 Supported by the Division of Biological Energy Conversion and Conservation, Office of Basic Energy Sciences, United States Department of Energy under Contract No. W-7405-ENG-48, and by a Rockefeller Foundation Postdoctoral Fellowship (to A. L. L.).






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1982 by the American Society of Plant Biologists