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1.
Direct evidence is presented for a proline cycle using a cell-free experimental system which sequentially transfers 3H from [1-3H]glucose to NADP+ to Δ1-pyrroline-5-carboxylate and yields [3H]proline. The formation of [3H]proline depends on the presence of NADP, Δ1-pyrroline-5-carboxylate, and the enzymes glucose-6-phosphate dehydrogenase and Δ1-pyrroline-5-carboxylate reductase. The production of [3H]proline from unlabeled proline in the presence of mitochondria provides direct evidence for one complete turn of a proline cycle which transfers reducing equivalents produced by glucose oxidation in the pentose pathway into mitochondria. In this cycle, proline is oxidized to Δ1-pyrroline-5-carboxylate by mitochondrial proline oxidase. Δ1-pyrroline-5-carboxylate is released from mitochondria and is recycled back to proline by Δ1-pyrroline-5-carboxylate reductase with concomitant oxidation of NADPH. At the maximal rate observed, 60% of Δ1-pyrroline-5-carboxylate produced is recycled back to proline. This cycle provides a mechanism for transferring reducing equivalents from NADPH into mitochondria and is linked to glucose oxidation in the pentose pathway by NADPH turnover. 相似文献
2.
J M Phang S J Downing G C Yeh R J Smith J A Williams 《Biochemical and biophysical research communications》1979,87(2):363-370
L-pyrroline-5-carboxylic acid, an intermediate in the interconversions of glutamic acid, ornithine and proline, is a potent stimulator of the hexose-monophosphate pentose pathway in cultured human fibroblasts. These studies suggest that pyrroline-5-carboxylate reductase, which catalyzes the conversion of pyrroline-5-carboxylate to proline coupled with the oxidation of NADPH, provides the NADP for the observed activation of the hexose-monophosphate pentose pathway. 相似文献
3.
Stimulation of phosphoribosyl pyrophosphate and purine nucleotide production by pyrroline 5-carboxylate in human erythrocytes 总被引:6,自引:0,他引:6
Recent studies have shown that pyrroline 5-carboxylate, the intermediate in the interconversions of proline, ornithine, and glutamate, can regulate the metabolism of erythrocytes. We now report that the formation of 5-phosphoribosyl 1-pyrophosphate (PP-Rib-P) was markedly stimulated by pyrroline 5-carboxylate in intact red cells. The production of PP-Rib-P is an important point of regulation in nucleotide metabolism. We found that pyrroline 5-carboxylate increased glucose metabolism through the oxidative arm of the pentose shunt, ribose 5-phosphate formation, and PP-Rib-P production and subsequently augmented purine nucleotide production through the salvage pathway in erythrocytes. We now report that pyrroline 5-carboxylate markedly stimulated the net synthesis of inosine monophosphate from hypoxanthine in intact human red cells so that the pool of inosine monophosphate became 20-30% of the total pool of purine nucleotides. Inosine monophosphate has been considered to be a "mobile pool" of purines, i.e. a reservoir from which peripheral tissues can be supplied; the effect of pyrroline 5-carboxylate on the inosine monophosphate pool may be a mechanism for regulating the function of erythrocytes in purine delivery. 相似文献
4.
5.
Recent years have seen the convergence of both genetic and biochemical approaches in the study of protein translocation inE. coli. The powerful combination of these approaches is exemplified in the use of anin vitro protein synthesis-protein translocaltion system to analyze the role of genetically defined components of the protein translocation machinery. We describe in this review recent results focusing on the function of thesecA, secB, andsecY gene products and the demonstration of their requirement forin vitro protein translocation. The SecA protein was recently shown to possess ATPase activity and was proposed to be a component of the translocation ATPase. We present a speculative working model whereby the translocator complex is composed of the integral membrane proteins SecY, SecD, SecE, and SecF, forming an aqueous channel in the cytoplasmic membrane, and the tightly associated peripheral membrane protein SecA functioning as the catalytic subunit of the translocator or protein-ATPase. 相似文献
6.
Transfer of 1-pyrroline-5-carboxylate as oxidizing potential from hepatocytes to erythrocytes. 总被引:2,自引:0,他引:2 下载免费PDF全文
The interconversions of proline and 1-pyrroline-5-carboxylate form an intercellular cycle that is the basis of a metabolic interaction between hepatocytes and erythrocytes. The cycle transfers oxidizing potential from hepatocytes to erythrocytes, which stimulates pentose phosphate pathway in erythrocytes. This interaction depends on the differential metabolism of proline and 1-pyrroline-5-carboxylate in erythrocytes and hepatocytes and consists of the following: in hepatocytes proline oxidase converts proline into 1-pyrroline-5-carboxylate, which is released into the medium and taken up by erythrocytes; erythrocyte 1-pyrroline-5-carboxylate reductase converts 1-pyrroline-5-carboxylate into proline and concomitantly generates NADP+; the generated oxidizing potential drives glucose metabolism through the pentose phosphate pathway in erythrocytes; finally, erythrocytes release proline into the medium, enabling it to re-enter hepatocytes and repeat the cycle. The increased activity of the pentose phosphate pathway in erythrocytes may enhance the production of 5-phosphoribosyl pyrophosphate, a necessary moiety for the processing of purines. 相似文献
7.
James M. Phang Sylvia J. Downing Grace Chao Yeh 《Biochemical and biophysical research communications》1980,93(2):462-470
The reactions catalyzed by proline oxidase and pyrroline-5-carboxylate reductase form a catalytic cycle linking the hexose-monophosphate pentose (HMP) pathway to mitochondrial ATP generation. The cycling of proline and pyrroline-5-carboxylate couples glucose oxidation to ATP generation by a mechanism independent of the Embden-Meyerhof pathway and the tricarboxylic acid cycle. 相似文献
8.
Addition of Rapamycin to Anti-CD3 Antibody Improves Long-Term Glycaemia Control in Diabetic NOD Mice
Shira Perl Jordan Perlman R. P. Weitzel Oswald Phang Matthew M. Hsieh John Tisdale 《PloS one》2013,8(6)
Aims/Hypothesis
Non-Fc-binding Anti CD3 antibody has proven successful in reverting diabetes in the non-obese diabetes mouse model of type 1 diabetes and limited efficacy has been observed in human clinical trials. We hypothesized that addition of rapamycin, an mTOR inhibitor capable of inducing operational tolerance in allogeneic bone marrow transplantation, would result in improved diabetes reversal rates and overall glycemia.Methods
Seventy hyperglycemic non-obese diabetic mice were randomized to either a single injection of anti CD3 alone or a single injection of anti CD3 followed by 14 days of intra-peritoneal rapamycin. Mice were monitored for hyperglycemia and metabolic control.Results
Mice treated with the combination of anti CD3 and rapamycin had similar rates of diabetes reversal compared to anti CD3 alone (25/35 vs. 22/35). Mice treated with anti CD3 plus rapamycin had a significant improvement in glycemia control as exhibited by lower blood glucose levels in response to an intra-peritoneal glucose challenge; average peak blood glucose levels 30 min post intra-peritoneal injection of 2 gr/kg glucose were 6.9 mmol/L in the anti CD3 plus rapamycin group vs. 10 mmo/L in the anti CD3 alone (P<0.05).Conclusions/Interpretation
The addition of rapamycin to anti CD3 results in significant improvement in glycaemia control in diabetic NOD mice. 相似文献9.
10.
Oregon‐R, +3, and crossbred strains of Drosophila melanogaster were tested for their response to selection for abdominal bristle number. Various subsidiary tests, consisting of heritability estimations, testing for lethal second and third chromosomes, and chromosome assays were conducted on the selection replicates, which had undergone 14 generations of selection. Evidence showed that a plateau which occurred very early in the +3 high selection replicates was due to fixation of a few additive genes with large effects, thus accounting for the low phenotypic and additive genetic variance, the slight regression in abdominal bristle number on relaxation of selection, the absence of directional dominance, and the low frequency of recessive lethals. High frequencies of second and third chromosome lethals were found in the Oregon‐R high and low replicates and in the +3 low replicates. That these lethals were not selected for heterozygote superiority for extreme bristle effect was indicated by the slight regression of these replicates on relaxation of selection, and by the absence of high, fluctuating phenotypic variances. From chromosome assays it appears that the two parental strains had different arrays of genes affecting high bristle number, with these genes located mostly in chromosome II in the Oregon‐R high line but in chromosome III in the +3 high line. In the Crossbred high line, high bristle factors were located in both the second and third chromosomes. The low bristle factors were located mainly in the second chromosome in all three low selection lines. It appears that the original cross had combined different genes favouring high bristle number, thus allowing greater response in the Crossbred high selection line. The same did not occur for low selection; the response from the Crossbred low line was similar to that of the parental low lines, suggesting that the gene arrays affecting low bristle number in the two original populations were comparable. 相似文献