Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0016382 (flushing)
 6,387 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The (12)CO2- and (14)CO2-exchange of illuminated corn leaf discs were measured at normal (21%) and low (1%) oxygen. After periods of exposure to (14)CO2 or to (14)CO2 followed by (12)CO2, the discs were killed and the specific activities of some metabolites were determined. At both O2 concentrations the specific activity of 3-PGA increased and decreased rapidly during the first 5 min of (14)CO2-feeding or (12)CO2-flushing but did not equilibrate with that of the CO2 in the assimilation chamber even after 15 min. The specific activity of aspartic acid also showed bimodal kinetics during both feeding and flushing. The specific activities of 3-phosphoglyceric acid (3-PGA), aspartic acid and alanine were higher at 1% O2 than at 21% O2, but glycine and serine were lower in specific activity at 1% O2. The results are in agreement with the proposed initial fixation of CO2 into C4-dicarboxylic acids and subsequent transfer of this carbon to 3-PGA. Indirect evidence supports the idea that at 21% O2, CO2 was produced by the corn leaf discs in the light and was refixed into C4-dicarboxylic acids. At 1% O2, the photorespiratory process could also have been active although the flux of carbon through the glycolate pathway was probably smaller than at 21% O2.
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PMID:Changes in specific radioactivities of corn-leaf metabolites during photosynthesis in (14)CO 2 and (12)CO 2 at normal and low oxygen. 2444 50

Sunflower (Helianthus annuus L.) leaf discs were exposed to (14)CO2 or (14)CO2 followed by (12)CO2 in an open gas-exchange system with incoming gas of approximately 400 ppm CO2 and either 21% or 1% O2. The (14)CO2 and (12)CO2 gas-exchange of the leaf discs were measured, and the specific activities of several metabolites were determined after different lengths of time. The rate of CO2 efflux by the leaf discs was ca. 20% of the net photosynthetic rate at 21% O2 but no CO2 efflux could be detected at 1% O2. At both O2 concentrations the specific activity of 3-phosphoglyceric acid (3-PGA) increased and decreased rapidly for the first 5 min, and then more slowly during (14)CO2 feeding and (12)CO2 flushing. At 21% O2, glycine, serine and alanine changed more slowly in specific activity than 3-PGA and at 1% O2 their specific activities were much lower than at 21% O2. The results at both O2 concentrations indicated that the glycolate pathway compounds were not derived solely from Calvin-cycle intermediates. At 1% O2 the flux of carbon from the immediate fixation products was inhibited and serine was at least partially produced from a precursor of higher specific activity than glycine, although the glycolate pathway may have been active even at 1% O2. The difference between the specific activities of 3-PGA and the feeding gases could be explained by the recycling of C from the glycolate pathway.
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PMID:Changes in specific radioactivities of sunflower leaf metabolites during photosynthesis in (14)CO 2 and (12)CO 2 at normal and low oxygen. 2444 51