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Sumio Asami, Takashi Akazawa, Biosynthetic mechanism of glycolate in Chromatium 6. Glycolate formation and metabolism under low O21, Plant and Cell Physiology, Volume 19, Issue 8, December 1978, Pages 1353–1362, https://doi.org/10.1093/oxfordjournals.pcp.a075719
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Abstract
Under low O2 (0.05 mM O2), there was no measurable excretion of glycolate or glycine by Chromatium cells, unlike the case of their incubation under high (0.7 mM) O2 However, upon addition of non-radioactive glycolate and glycine to the suspension medium, there occurred a measurable incorporation of 14CO2 into these compounds, which were then excreted extracellularly; the total radioactivities measured were approximately 15% of the total CO2 fixed photosynthetically. This phenomenon could be as cribed to the dilution of the intracellular pools by the compounds added. The results indicate that under low O2 the glycolate molecules produced are metabolically further transformed in the bacterial cells. The incorporation of 14CO2 into the extracellular glycolate fraction was maximal at 0.3 mM glycolate in both high and low O2. Presumably, glycolate formed in the bacterial cells under both the high and low O2 is metabolized in a similar manner, although the excess glycolate and glycine molecules are rapidly excreted. During glycolate metabolism CO2 was evolved from an isonicotinylhydrazide-sensitive reaction, suggesting that the pathway <glycolate → glycine →. CO2 was similar in green plants. The results thus indicate that studies on glycolate and glycine metabolism in the anaerobic bacterium, Chromatium, provide a useful model system for elucidating the mechanism of photorespiration in green plants.
