Substrate specificity of the pea chloroplast glycolate transporter

The transport of glycolic acid across the chloroplast envelope is a mediated pr ocess. Out of a number of metabolites assayed, only two or three carbon 2-hydroxymonocarboxylates significantly inhibited ( super(14)C)glycolate uptake by intact pea choroplasts. These compounds were found to be competit...

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Bibliographic Details
Published in:Biochemistry (Easton) 1985-07, Vol.24 (14), p.3645-3650
Main Authors: Howitz, Konrad T, McCarty, Richard E
Format: Article
Language:English
Subjects:
Biological and medical sciences
Cell physiology
chloroplasts
composicion
composition
Fundamental and applied biological sciences. Psychology
glycolic acid
Membrane and intracellular transports
Molecular and cellular biology
Pisum sativum
plantas
plante
plants
plaste
plastidios
plastids
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Summary:The transport of glycolic acid across the chloroplast envelope is a mediated pr ocess. Out of a number of metabolites assayed, only two or three carbon 2-hydroxymonocarboxylates significantly inhibited ( super(14)C)glycolate uptake by intact pea choroplasts. These compounds were found to be competitive inhibitors of glycolate uptake, with D-glycerate, D-lactate, and glyoxylate having K sub(i)'s approximately equal to the K sub(m) for uninhibited glycolate uptake. L-Glycerate was less inhibitory than D-glycerate, and L-lactate did not appear to inhibit glycolate uptake. D-Glycerate, D-lactate, and glyoxylate caused countertransport of labeled glycolate, indicating that they are transportable substrates of the glycolate carrier. Glycolate and D-glycerate behaved similarly with respect to N-ethylmaleimide inhibition of their ability to increase the pH of the medium of a weakly buffered chloroplast suspension. It is concluded that glycolate and D-glycerate, substrate and product, respectively, of the photorespiratory carbon cycle, are transported by the same carrier.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00335a037