Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00790 (PGA)
 2,475 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The high oxygen affinity of fetal blood in rabbits is due to a very low concentration of 2,3-diphosphoglycerate (2,3-DPG) in the red cells. In order to gather informations on the factors responsible for this characteristic we have studied synthesis and break-down of 2,3-DPG in fetal and adult rabbit red cells in vitro and examined possible regulative pathways which may lead to the low 2,3-DPG concentration in vivo. 2. Under conditions where 2,3-DPG and 3-phosphoglycerate (3-PGA) accumulate in adult erythrocytes, i.e. in a solution containing inosine, pyruvate and inorganic phosphate, the amount of 2,3-DPG synthetized in fetal red cells was only 40% of the adult value and 3-PGA was not measurable. Upon inhibition of enolase by NaF, however, both 2,3-DPG and 3-PGA increased to a similar extent in fetal and adult red cells. These findings point towards differences in the pyruvate kinase (PK) reaction which is one of the rate limiting steps of glycolysis. Direct measurements revealed an over tenfold higher PK activity in fetal compared to adult red cells. This higher activity of PK will lead to a decreased concentration of 3-PGA with a consecutive fall in 2,3-DPG concentration. 3. Other factors, like a decreased glucose utilization, a decreased activity of 2,3-DPG mutase or an increased 2,3-DPG phosphatase activity could be excluded as a cause for the low 2,3-DPG concentration in fetal red blood cells. The same holds for extraerythrocytic factors like glucose concentration or pH value in fetal blood. 4. During the postnatal development of rabbits the PK activity decreased. 50 days after birth, PK activity was 20% of the fetal value but still somewhat higher than in adult erythrocytes. This change is paralleled by an increase in 2,3-DPG concentration and half saturation oxygen pressure. With respect to the synthesis of 2,3-DPG and ATP, the fetal rabbit red cell is comparable to hereditary high PK activity in human erythrocytes.
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PMID:High pyruvate kinase activity causes low concentration of 2,3-diphosphoglycerate in fetal rabbit red cells. 2 78

Responses of foliar and isolated intact chloroplast photosynthetic carbon metabolism observed in spinach (Spinacia oleracea cv Wisconsin Bloomsdale) plants exposed to a shortened photosynthetic period (7-hour light/17-hour dark cycle), were used as probes to examine in vivo metabolic factors that exerted rate determination on photosynthesis (PS) and on starch synthesis. Compared with control plants propagated continuously on a 12-hour light/12-hour dark cycle, 14 to 15 days were required, subsequent to a shift from 12 to 7 hours daylength, for 7-hour plants to begin to grow at rates comparable to those of 12-hour daylength plants. Because of shorter daily durations of PS, daily demand for photosynthate by growth processes appeared to be greater in the 7-hour than in the 12-hour plants. The result was that 7-hour plants established a 1.5- to 2.0-fold higher total PS rate than 12-hour plants.Intact chloroplasts isolated from the leaves of 7-hour plants (7-h PLD) displayed 1.5- to 2.0-fold higher PS rates than plastids isolated from 12-hour plants (12-h PLD). Plastid lamellae prepared from 7- and 12-h PLD isolates displayed equivalent rates of ferredoxin-dependent ATP and NADPH photoformation indicating that electron transport processes were not factors in the establishment of higher 7-h PLD PS rates. Analyses, both in leaves as well as intact PLD isolates, of dark to light transitional increases in Calvin cycle intermediates, e.g., ribulose-1,5-bisphosphate (RuBP) and 3-phosphoglycerate (3-PGA), as well as estimations of activities of RuBP carboxylase and fructose-1,6-bisphosphate phosphatase, indicated that 7-hour plant leaves displayed higher PS rates (than 12-hour plants), because there was a higher magnitude of activity of the Calvin cycle.Although both the foliar level of starch and sucrose, as well as starch synthesis rate, often was higher in 7-hour compared with 12-hour plant foliage, the higher 7-hour plant total PS rates indicated that maximal sucrose and starch levels did not mediate any ;feedback' inhibition of PS. The higher 7-hour plant foliar and PLD PS rates resulted in higher glucose-1-P levels as well as a higher ratio of 3-PGA:Pi, both factors of which would enhance the activity of chloroplast ADP-glucose pyrophosphorylase, and which were attributed to be causal to the higher starch synthesis rates observed in 7-hour plant foliage and PLD isolates.
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PMID:Photosynthetic Carbon Metabolism in Leaves and Isolated Chloroplasts from Spinach Plants Grown under Short and Intermediate Photosynthetic Periods. 1666 34