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

An enzyme capable of hydrolyzing the substrate L-alanine p-nitroanilide has been found in the various Escherichia coli strains tested. This enzyme has been called aminoendopeptidase since it shows both activities (see accompanying paper). It is released from the cells by osmotic shock and by lysozyme -- EDTA spheroplasting treatment, and 50% of the total activity is directly detectable with suspensions of intact cells. However, the release by osmotic shock or spheroplasting is not as efficient as it is for alkaline phosphatase. This periplasmic aminoendopeptidase is constitutively produced but the differential rate of synthesis is increased 4-fold when the cell growth is limited by Pi. The occurrence of this 'derepression' is simultaneous with that of alkaline phosphatase. Increasing the concentration of inorganic phosphate in the medium has no effect on the constitutive aminoendopeptidase synthesis. The effect of phosphate starvation is specific since starvation for neither nitrogen nor carbon and energy source are effective in derepressing aminoendopeptidase.
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PMID:Evidence for an aminoendopeptidase localized near the cell surface of Escherichia coli. Regulation of synthesis by inorganic phosphate. 110 39

To evaluate the role of hyperketonemia in the hypoalaninemia and decreased protein catabolism of prolonged starvation, Na dl-beta-hydroxybutyrate was administered as a primed continuous 3-6-h infusion in nonobese subjects and in obese subjects in the postabsorptive state and after 3 days and 3-5 1/2 wk of starvation. An additional obese group received 12-h ketone infusions on 2 consecutive days after 5-10 wk of fasting. The ketone infusion in nonobese and obese subjects studied in the postabsorptive state resulted in total blood ketone acid levels of 1.1-1.2 mM, a 5-15 mg/100 ml decrease in plasma glucose, and unchanged levels of insulin, glucagon, lactate, and pyruvate. Plasma alanine fell by 21% (P smaller than 0.001) in 3 h. In contrast, other amino acids were stable or varied by less than 10%. Infusions lasting 6 h reduced plasma alanine by 37%, reaching levels comparable to those observed in prolonged starvation. Equimolar infusions of NaC1 and/or administration of NaHCO3 failed to alter plasma alanine levels. During prolonged fasting, plasma alanine, which had fallen by 40% below prefast levels, fell an additional 30% in response to the ketone infusion. In association with repeated prolonged (12 h) infusions in subjects fasted 5-10 wk, urinary nitrogen excretion fell by 30%, returning to base line after cessation of theinfusions and paralleling the changes in plasma alanine. Ketone infusins resulted in two- to fourfold greater increments in blood ketone acids in fasted as compared to postabsorptive subjects. It is concluded that increased blood ketone acid levels induced by infusions of Na DL-beta-hydroxybutyrate result in hypoalaninemia and in nitrogen conservation in starvation. These data suggest that hyperketonemia may be a contributory factor in the decreased availability or circulating alanine and reduction in protein catabolism characteristic of prolonged fastings9
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PMID:Effect of ketone infusions on amino acid and nitrogen metabolism in man. 113 79

The 3-day-old rat has a high basal level of phosphoenolpyruvate carboxykinase (PEPCK), the activity of which is not increased upon starvation. The lower basal activity of the enzyme in 19-day-old rat liver can, however, be stimulated by starvation. Serum glucose levels increased from 3 days to 19 days of age, with a decrease to adult levels. Liver glycogen concentration increased from 3 days to 19 days of age, with no additional increase observed at 3 months. There was a decrease with age in the specific activity of liver glycogen (from [14C]alanine and [14C]leucine). In fed rats given [14C]alanine, 14CO2 expiration tended to decrease with age. The 14CO2 production from [14C]leucine was less than that from alanine, and also decreased with age. Three-day-old rats showed no change in serum glucose when starved for 4 hr. On the other hand, 19-day-old rats responded with a decrease in serum glucose; although the adult animal's basal level of serum glucose was less than that of the 19-day-old rats, starvation for 15 hr also caused a significant decrease. There was no statistically significant difference in liver glycogen concentration between the fed and starved 3-day-old animals. Liver glycogen concentration in the 19-day-old adult rats was affected, however, by starvation. The 3-day-or glycogen during starvation. Starvation resulted in a tremendous increase in the specific activity of hepatic glycogen in the 19-day-old and adult rats. Starvation decreased the percentage of labeled amino acid expired as 14CO2. The proportion expired also decreased with age. Urinary nitrogen concentration increased significantly between 3 and 19 days of age. Starvation produced differential effects in the animals, with no change being observed in either the 3-day or adult rats; a decrease was observed in the 19-day-old animals. Urinary nitrogen concentration was measured in adult carbohydrate-deprived rats and was significantly higher than control values. These rats had a high gluconeogenic rate, reflected in the increased urinary nitrogen concentration. The young rat is at the mercy of a continuous supply of substrate in that it has a limited capacity for directing substrat
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PMID:Utilization of dietary amino acids for energy production in neonatal rat liver. 125 Jun 45

A reduction in the release of substrate amino acids from skeletal muscle largely explains the decrease in gluconeogenesis characterizing prolonged starvation. Brief starvation is associated with an increase in gluconeogenesis, suggesting increased release of amino acids from muscle. In the present studies, accelerated amino acid release from skeletal muscle induced by brief starvation was sought to account for the accompanying augmentation of gluconeogenesis. To do this amino acid balance across forearm muscles was quantified in 15 postabsorptive (overnight fasted) subjects and in 7 subjects fasted for 60 h. Fasting significantly reduced basal insulin (11.3-7.5 muU/ml) and increased glucagon (116-134 pg/ml). Muscle release of the principal glycogenic amino acids increased. Alanine release increased 59.4%. The increase in release for all amino acids averaged 69.4% and was statistically significant for threonine, serine, glycine, alanine, alpha-aminobutyrate, methionine, tyrosine, and lysine. Thus, with brief starvation, muscle release of glycogenic amino acids increases strikingly. This contrasts with the reduction of amino acid release characterizing prolonged starvation. The adaptation of peripheral tissue metabolism to brief starvation is best explained by the decrease in insulin.
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PMID:Effects of brief starvation on muscle amino acid metabolism in nonobese man. 125 28

Following an oral 14C-alanine load, obese Zucker rats showed the same rate of intestinal amino acid absorption as their lean counterparts. Alanine absorption was unchanged by a 24 h starvation period. The whole-body oxidation of the absorbed tracer was lower in the fa/fa rats and was significantly decreased in both lean and obese groups when the animals were submitted to starvation. The incorporation of the 14C-tracer into 14C-lipid was significantly higher in the carcass, skeletal muscle, white adipose tissue and liver of the obese animals, while that of brown adipose tissue was decreased as compared to that of the lean rats. Starvation induced no variation in 14C-lipid incorporation in the lean (+/?) animals while it sharply decreased this parameter in the obese. The incorporation of the tracer into 14C-glycogen and 14C-protein was also increased in the liver of the obese rats while no changes in incorporation into these fractions were observed in skeletal muscle. It is concluded that dietary amino acids significantly contribute to the hyperlipogenesis found in the liver and adipose tissue of the fa/fa rats.
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PMID:The metabolic fate of an oral 14C-alanine load in the obese Zucker rat. 131 31

The isoform of cytochrome P450 that catalyzes the 12 alpha-hydroxylation of 7 alpha-hydroxy-4-cholesten-3-one, an intermediate in the conversion of cholesterol to cholic acid, was purified to homogeneity from rabbit liver microsomes. The extent of purification in the various steps was judged by an assay involving high performance liquid chromatography. The purified enzyme showed a single band on SDS-polyacrylamide gel electrophoresis (M(r) = 50,000). The NH2-terminal amino acid sequence is as follows: Val-Leu-Trp-Gly-Leu-Leu-Gly-Ala-Leu-Leu-Met-Val-Met-Val-Gly-, which is different from that of any other P450s so far reported. The specific content of the enzyme was 13.3 nmol of cytochrome P450/mg of protein. Upon reconstitution with NADPH-cytochrome P450 reductase and cytochrome b5, the P450 enzyme showed a high activity of 12 alpha-hydroxylation with a turnover number of 36.6 min-1 at 37 degrees C. The omission of either cytochrome P450 or NADPH-cytochrome P450 reductase resulted in complete loss of activity, and the omission of cytochrome b5 resulted in 40% loss of activity. Antibodies prepared from mouse inhibited the 12 alpha-hydroxylase activity of rabbit liver microsomes about 90% and that of the rat liver microsomes 50%. The enzyme activity was not inhibited by other antibodies raised against other forms of P450 that catalyze different monooxygenation reactions toward xenobiotics or endogenous substrates. Anti-cytochrome b5 antibody inhibited the activity 40%, suggesting the functional role of this protein, and anti-reductase inhibited the activity almost completely. The microsomal enzyme activity was markedly elevated by starvation or streptozotocin administration to the animals. However, an immunoblotting experiment showed no correlation between the enzyme activity and the amount of protein, suggesting that post-translational modification may occur.
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PMID:Purification and characterization of 7 alpha-hydroxy-4-cholesten-3-one 12 alpha-hydroxylase. 140 Apr 44

Kinetics of intestinal transport of L-alanine and L-valine (substrates of the A-system and the L-system, respectively, in mammals) across the brush-border membrane in sea bass, Dicentrarchus labrax, were studied on intact mucosa using a short-term uptake technique. When fish were starved for 4-8 weeks, total influx (mucosa-to-cell) of valine fell owing to disappearance or modification of the diffusion component. The maximum influx rate of saturable component increased but its affinity (reflected by the Michaelis constant) decreased. Alanine transport by Na(+)-dependent and diffusion pathways was unchanged after starvation. Fasting also induced an almost 20% decrease in the length of intestinal microvilli.
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PMID:Effects of starvation on valine and alanine transport across the intestinal mucosal border in sea bass, Dicentrarchus labrax. 140 35

The present study was designed to investigate the metabolism of glycylglutamine and its effects on organ balances of amino acids during intravenous infusion of this dipeptide (100 mumol.h-1.kg-1) in postabsorptive and briefly starved (84-86 h) human subjects. Arterial concentrations of glycylglutamine were not significantly different in postabsorptive (265 +/- 18 microM) and starved (241 +/- 13 microM) subjects. Among the organs examined, kidney predominated in clearance of glycylglutamine from plasma. Moreover, renal clearance of glycylglutamine was reduced by starvation (87 +/- 7 vs. 52 +/- 5 mumol/min, P less than 0.01), whereas neither splanchnic nor muscle clearance was significantly affected. Infusion of glycylglutamine raised plasma concentrations of glycine and glutamine by increasing renal release of these amino acids. In postabsorptive subjects the infusion significantly increased splanchnic balances of glycine and glutamine with little or no effect on the muscle balances; the opposite was found in starved subjects. As far as other amino acids are concerned, the infusion decreased the muscle release of alanine and increased renal release of serine. We conclude that the amino acid residues of glycylglutamine are largely metabolized by the splanchnic organs in postabsorptive subjects and by peripheral organs in starved subjects. The latter results in selective inhibition of muscle release of amino acids.
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PMID:Glycylglutamine: metabolism and effects on organ balances of amino acids in postabsorptive and starved subjects. 153 41

Measurements of the tissue accumulation of alpha-amino[1-14C]isobutyrate [1-14C]AIB in lean (+/?) and obese (fa/fa) Zucker rats showed an augmented tissue/plasma ratio in the liver of the obese animals. In contrast, brown adipose tissue AIB accumulation was lower in the fa/fa animals. In response to a 24 h starvation period AIB accumulation was significantly elevated in the liver and plasma of the lean animals and was unchanged in the liver of the fa/fa animals. The circulating concentration of alanine and branched-chain amino acids was elevated in the fa/fa animals as compared to their lean counterparts. These observations suggest that amino acid uptake is not involved in the impaired muscle development observed in the obese Zucker rat and that the ability of brown adipose tissue for amino acid utilization is decreased in the obese animals suggesting that this may partially explain the impaired thermoregulatory capacity observed in brown adipose tissue of obese Zucker rats.
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PMID:Amino acid metabolism in several tissues of the obese Zucker rat as indicated by the tissue accumulation of alpha-amino[1-14C]isobutyrate. 158 4

We show that phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2) by the protein kinase GCN2 mediates translational control of the yeast transcriptional activator GCN4. In vitro, GCN2 specifically phosphorylates the alpha subunit of rabbit or yeast eIF-2. In vivo, phosphorylation of eIF-2 alpha increases in response to amino acid starvation, which is dependent on GCN2. Substitution of Ser-51 with alanine eliminates phosphorylation of eIF-2 alpha by GCN2 in vivo and in vitro and abolishes increased expression of GCN4 and amino acid biosynthetic genes under its control in amino acid-starved cells. The Asp-51 substitution mimics the phosphorylated state and derepresses GCN4 in the absence of GCN2. Thus, an established mechanism for regulating total protein synthesis in mammalian cells mediates gene-specific translational control in yeast.
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PMID:Phosphorylation of initiation factor 2 alpha by protein kinase GCN2 mediates gene-specific translational control of GCN4 in yeast. 173 68


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