Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of alanine-, aspartate- and branched-chain amino-acid transaminases, glutamine synthetase, glutamate dehydrogenase and adenylate deaminase in white adipose tissue of adult male rats have been determined in animals submitted to 12-h cold exposure (4 degrees C) or to 24-h food deprivation. Starvation resulted in small changes in glutamate dehydrogenase and alanine transaminase when expressed per unit of protein weight, inducing an increase in branched-chain amino-acid transaminase and glutamine synthetase. Cold exposure showed the same effects as starvation with respect to glutamate dehydrogenase and alanine transaminase, but induced increases in glutamine synthetase and aspartate transaminase. It is concluded that starvation increases the handling of some amino acids by white adipose tissue and the detoxification of the ammonia thus evolved. The changes observed suggest a different pattern of amino-acid metabolism enzyme changes with either cold or starvation.
 ...
PMID:Amino-acid metabolism enzyme activities in rat white adipose tissue. 243 May 32

The GLN1 gene of Saccharomyces cerevisiae was cloned by complementation of a gln1 auxotroph. A GLN1-lacZ fusion was constructed to assay GLN1 promoter activity. beta-Galactosidase and glutamine synthetase expression in chromosomally integrated GLN1-lacZ fusion strains were co-regulated in response to a shift from glutamine to glutamate as the nitrogen source, purine limitation, and 3-aminotriazole-induced histidine starvation. Regulation of GLN1 expression by each of the three pathways occurred at the transcriptional level. Increased accumulation of GLN1 mRNA was observed within 5 min after a shift from glutamine to glutamate as the nitrogen source. After 5 min, GLN1 mRNA levels were constant. The level of GLN1 transcript was reduced by approximately 75% within 5 min following glutamine addition to the cells growing with glutamate as nitrogen source. This indicates that the GLN1 message is unstable and has a half-life of approximately 3 min. Deletion analysis indicated that the sequences required for GLN1 expression are located within approximately 350 bp upstream from the transcriptional initiation site.
 ...
PMID:Three regulatory systems control expression of glutamine synthetase in Saccharomyces cerevisiae at the level of transcription. 257 Mar 48

The state of adenylylation, n, of glutamine synthetase (GS) in Pseudomonas fluorescens has been determined as a function of growth conditions. Compared to the behavior of Escherichia coli, atypical responses to either carbon or nitrogen starvation were observed when P. fluorescens was grown with either succinate, malate, or fumarate as the sole source of carbon and energy. Under conditions of carbon starvation (high NH4+, low dicarboxylic acid substrate), the value of n falls rapidly from 10 to 1.0 during prolonged incubation in the stationary phase, whereas the value of n is unexpectedly high (ca. 10) in extracts of nitrogen-starved cells. These abnormal responses are attributable to particular permeability properties of P. fluorescens cells compared to E. coli. The unusual changes in nitrogen-starved cells are related to the release of alpha-ketoglutarate by such cells during incubation or washing procedures. These changes can be prevented by the addition of cetyltrimethylammonium bromide (CTAB) to the cultures 5 min prior to harvesting the cells, or by freezing the cell pellets just after centrifugation and sonication within 3 min of suspension in buffer, or by suspending freshly harvested cells in buffer containing alpha-ketoglutarate and orthophosphate (i.e., effectors that favor deadenylylation of glutamine synthetase). The abnormal changes which occur during carbon starvation in the presence of excess NH4+ can be prevented by addition of ATP and glutamine to the buffer in which the freshly harvested cells are suspended prior to sonication. The results suggest that during the stationary phase of growth on succinate, fumarate, or malate (but not on glucose), the cellular membrane becomes permeable to small molecules that regulate the adenylylation cascade, and indeed, it was observed that such whole cells expressed, without any chemical or physical treatment, more than 50% of the glutamine synthetase activity they contained. Such cells may be useful in studies to examine the effects of multiple metabolites on the regulation of glutamine synthetase adenylylation in situ.
 ...
PMID:Adenylylation state of glutamine synthetase and permeability properties of Pseudomonas fluorescens. 287 12

The activities of alanine and aspartate transaminases, adenylate deaminase, glutamine synthetase and glutamate and xanthine dehydrogenases have been measured in liver, yolk sac membrane, intestine and breast and leg muscle of domestic fowl hatchlings receiving for 3 or 5 days either a standard diet or hard boiled eggwhite as well as in 3 or 5 days starved animals. The patterns of activation of amino acid metabolism enzymes were fully comparable in protein-fed and starved groups with respect to fed controls; the differences with respect to the latter became more marked in 5- than in 3-days old chicks. In 5-days old chicks intestine alanine transaminase activity increased in parallel to that of liver in protein-fed animals but not in those starved, in agreement with an enhanced alanine transfer between both organs under this situation. Both, starvation and protein-feeding, induced a general decrease in the amino acid metabolizing ability of muscle. Glutamine (but not alanine) synthetizing capabilities were enhanced.
 ...
PMID:Effect of starvation and a protein diet on the amino acid metabolism enzyme activities of the organs of domestic fowl hatchlings. 287 42

The effect of 24-hr starvation on the amino acid pool composition and its concentration ratios with respect to blood and plasma as well as the activities of alanine, aspartate and branched chain amino acid transaminases, glutamate dehydrogenase, glutamine synthetase and adenylate deaminase have been studied in rat brown adipose tissue. Starvation induced a considerable decrease of pool amino acid concentration. Alanine and taurine were the amino acids in which the decrease was more marked. Small changes were observed in the activities of the enzymes studied, with decreases only in glutamate dehydrogenase and adenylate deaminase. These changes agree with a decrease in amino acid utilization in this tissue induced by starvation.
 ...
PMID:Effect of 24-hour starvation on amino acid pool composition and enzyme activities of rat brown adipose tissue. 288 93

The influence of glucocorticoids on muscle glutamine production in starvation was studied by using cortisol-treated or non-cortisol-treated, starved, adrenalectomized rats. Administration of cortisol at physiological doses in vivo (1 mg/100 g body weight) to fasted, adrenalectomized rats increased the muscle ratio of glutamine/glutamate and the activity of glutamine synthetase after only 6 hours. Prior treatment of fasted, adrenalectomized animals with actinomycin D or proflavine abolished these increases by cortisol. Therefore, cortisol induces muscle glutamine synthetase, and this induction can be detected by changes in the fresh-muscle ratio of glutamine/glutamate. Using this ratio as a qualitative indicator of muscle glutamine synthesis, the role of glucocorticoids in modifying muscle glutamine production in starvation was studied. In fresh-frozen soleus, extensor digitorum longus, and diaphragm muscle, starvation led to greater ratios of glutamine/glutamate and higher levels of tyrosine, which are indicative of enhanced muscle protein turnover. These effects were not apparent in starved, adrenalectomized animals but were restored, at least partially, by administering a physiological dose of cortisol. Therefore, glucocorticoids seem essential for promoting muscle glutamine production in starvation probably by inducing the activity of glutamine synthetase.
 ...
PMID:Role of glucocorticoids in increased muscle glutamine production in starvation. 290 Apr 64

The liver is the "glucostat" of the organism and serves at the same time as an "ammonia-sink and pH stat". The key enzymes involved in glucose uptake and release and in urea and glutamine formation are reciprocally distributed over the liver parenchyma: The glucogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK), fructosebisphosphatase (FBPase) and glucose-6-phosphatase (G6Pase) as well as the ureagenic enzyme carbamoylphosphate synthetase (CAPS) are predominant in the periportal zone. The glycolytic enzymes glucokinase (GK) and pyruvate kinase type L (PKL) as well as the glutaminogenic enzyme glutamine synthetase (GluNS) are prevalent in the perivenous zone. This heterogeneity appears to be a prerequisite for the normal "glucostat, ammonia-sink and pH-stat" function of the liver. After birth the liver is a gluconeogenic organ, only with weaning it becomes a "glycolytic/gluconeogenic" glucostat. In the rat zonation of PEPCK, G6Pase and CAPS developed gradually after birth and was completed before weaning, i.e. before it would be functionally required. After 2/3 partial hepatectomy the liver looses its normal glucostat function and becomes a gluconeogenic organ. With this change the zonation of PEPCK and PKL were also lost; it was restored only during the second week after operation. During starvation the liver also looses its glucostat function to become the major glucose supplier of the organism. Zonation of PEPCK and PKL were diminished to such an extent that the major function of the perivenous zone was altered from glucose uptake to release. In diabetes the liver does not loose its glucostat function; however, the function is severely impaired. Zonation of PEPCK was increased and that of PKL decreased in such a manner that the major function of the perivenous zone, glucose uptake, was not entirely changed but only diminished. It can be concluded that in the various physiological states studied the zonation of enzymes correlated well with the glucostat function of the liver.
 ...
PMID:Dynamics of zonal hepatocyte heterogeneity. Perinatal development and adaptive alterations during regeneration after partial hepatectomy, starvation and diabetes. 301 Mar 76

The photosynthetic bacterium Rhodospirillum rubrum regulates the activity of its nitrogenase (N2ase) by interconverting the enzyme into three distinct enzymatic species: N2ase A (a fully active form) and two regulatory forms, N2ase Ractive and N2ase Rinactive. N2ase R is distinguished from N2ase A in vitro by the requirement of its Fe protein for activation by a Mn2+-dependent activating factor. N2ase is converted from the A to the R form in response to certain environmental factors such as carbon starvation, depletion of intracellular adenosine triphosphate, or the addition of NH4+ (or glutamate) to a culture of N-starved cells. The rapid inhibition of R. rubrum N2ase in vivo by NH4+ was shown to result from the conversion of N2ase A to N2ase Rinactive. On depletion of NH4+ from the culture, whole-cell N2ase activity returned; however, the enzyme remained in the R form. Unlike the effect of NH4+, adding glutamate to cells containing N2ase A did not inhibit in vivo activity, but converted the enzyme to the R form (N2ase Ractive). Although glutamate-induced N2ase R formation was much slower than the NH4+-induced reaction, it occurred in the presence of rifampin, indicating that de novo protein synthesis was not involved. This suggested that N2ase R was formed by a modification of N2ase A. Although glutamine synthetase in involved in the conversion of N2ase A to R, the adenylylation state of glutamine synthetase appears not to be involved in regulating this nitrogenase reaction.
 ...
PMID:Changes in the regulatory form of Rhodospirillum rubrum nitrogenase as influenced by nutritional and environmental factors. 610 95

Glutamine synthetase activity is modulated by nitrogen repression and by two distinct inactivation processes. Addition of glutamine to exponentially grown yeast leads to enzyme inactivation. 50% of glutamine synthetase activity is lost after 30 min (a quarter of the generation time). Removing glutamine from the growth medium results in a rapid recovery of enzyme activity. A regulatory mutation (gdhCR mutation) suppresses this inactivation by glutamine in addition to its derepressing effect on enzymes involved in nitrogen catabolism. The gdhCR mutation also increases the level of proteinase B in exponentially grown yeast. Inactivation of glutamine synthetase is also observed during nitrogen starvation. This inactivation is irreversible and consists very probably of a proteolytic degradation. Indeed, strains bearing proteinase A, B and C mutations are no longer inactivated under nitrogen starvation.
 ...
PMID:Regulation of glutamine synthetase from Saccharomyces cerevisiae by repression, inactivation and proteolysis. 612 75

The specific inactivation of the uridylylation cycle of glutamine synthetase regulatory system occurring when E. coliW grown with limited nitrogen supply is subjected to permeabilization by Lubrol WX, is not strictly related to the nitrogen starvation at cell harvesting. Evidences indicating that the sensitivity of uridylylremoving-uridylyltransferase enzyme complex to detergent treatment is affected by both rate of growth and cellular yield of the culture, are presented.
 ...
PMID:Growth conditions and inactivation of the uridylylation cycle of the glutamine synthetase regulatory system in permeabilized cells of E. coli. 612 7


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>