Biosynthetic mechanism of glycolate in Chromatium 6. Glycolate formation and metabolism under low O21 |
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Authors: | Asami Sumio; Akazawa Takashi |
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Institution: | Research Institute for Biochemical Regulation, Nagoya University, School of Agriculture Chikusa, Nagoya 464, Japan |
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Abstract: | Under low O2 (0.05 mM O2), there was no measurable excretionof glycolate or glycine by Chromatium cells, unlike the caseof their incubation under high (0.7 mM) O2 However, upon additionof non-radioactive glycolate and glycine to the suspension medium,there occurred a measurable incorporation of 14CO2 into thesecompounds, which were then excreted extracellularly; the totalradioactivities measured were approximately 15% of the totalCO2 fixed photosynthetically. This phenomenon could be as cribedto the dilution of the intracellular pools by the compoundsadded. The results indicate that under low O2 the glycolatemolecules produced are metabolically further transformed inthe bacterial cells. The incorporation of 14CO2 into the extracellularglycolate fraction was maximal at 0.3 mM glycolate in both highand low O2. Presumably, glycolate formed in the bacterial cellsunder both the high and low O2 is metabolized in a similar manner,although the excess glycolate and glycine molecules are rapidlyexcreted. During glycolate metabolism CO2 was evolved from anisonicotinylhydrazide-sensitive reaction, suggesting that thepathway <glycolate glycine . CO2 was similar in green plants.The results thus indicate that studies on glycolate and glycinemetabolism in the anaerobic bacterium, Chromatium, provide auseful model system for elucidating the mechanism of photorespirationin green plants. (Received May 19, 1978; ) |
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