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)

Repression of biosynthetic enzyme synthesis in Pseudomonas putida is incomplete even when the bacteria are growing in a nutritionally complex environment. The synthesis of four of the enzymes of the arginine biosynthetic pathway (N-acetyl-alpha-glutamokinase/N-acetylglutamate-gamma-semialdehyde dehydrogenase, ornithine carbamoyltransferase and acetylornithine-delta-transaminase) could be repressed and derepressed, but the maximum difference observed between repressed and derepressed levels for any enzyme of the pathway was only 5-fold (for ornithine carbamoyltransferase). No repression of five enzymes of the pyrimidine biosynthetic pathway (aspartate carbamoyltransferase, dihydro-orotase, dihydro-orotate dehydrogenase, orotidine-5'-phosphate pyrophosphorylase and orotidine-5'-phosphate decarboxylase) could be detected on addition of pyrimidines to minimal asparagine cultures of P. putida A90, but a 1-5- to 2-fold degree of derepression was found following pyrimidine starvation of pyrimidine auxotrophic mutants of P. putida A90. Aspartate carbamoyltransferase in crude extracts of P. putida A90 was inhibited in vitro by (in order of efficiency) pyrophosphate, CTP, UTP and ATP, at limiting but not at saturating concentrations of carbamoyl phosphate.
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PMID:Regulation of arginine and pyrimidine biosynthesis in Pseudomonas putida. 17 12

N-Acetylglutamate synthase, an early enzyme of the arginine pathway, provides acetylglutamate for ornithine synthesis in the so-called "acetylglutamate cycle." Because acetylglutamate is regenerated as ornithine is formed, the enzyme has only a catalytic or anaplerotic role in the pathway, maintaining "bound" acetyl groups during growth. We have detected this enzyme in crude extracts of Neurospora crassa and have localized it to the mitochondria along with other ornithine biosynthetic enzymes. The enzyme is bound to the mitochondrial membrane. The enzyme has a pH optimum of 9.0 and Km values for glutamate and CoASAc of 6.3 and 1.6 mM, respectively. It is feedback-inhibited by L-arginine (I0.5 = 0.16 mM), and its specific activity is augmented 2-3-fold by arginine starvation of the mycelium. Mutants of the newly recognized arg-14 locus lack activity for the enzyme. Because these mutants are complete auxotrophs, we conclude that N-acetylglutamate synthase is an indispensible enzyme of arginine biosynthesis in N. crassa. This work completes the assignment of enzymes of the arginine pathway of N. crassa to corresponding genetic loci. The membrane localization of the enzyme suggests a novel mechanism by which feedback inhibition might occur across a semipermeable membrane.
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PMID:N-acetyl-L-glutamate synthase of Neurospora crassa. Characteristics, localization, regulation, and genetic control. 293 69

Rats fasted for 3 and 6 days showed an increase in the activity, per g of liver but not per total liver, of the mitochondrial urea cycle enzymes, carbamylphosphate synthetase and ornithine transcarbamylase. The activity of N-acetylglutamate synthetase, both per g and per total liver, increased by the third day and then decreased on the sixth day of fasting. The cytosolic enzyme N-acetyldeacylase showed the same general pattern as the N-acetylglutamate synthetase except that the relative proportion of synthetase over deacylase was higher at the third day of starvation. The N-acetylglutamate level/g liver increases in relation to the number of days of fasting.
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PMID:Effect of starvation on the N-acetylglutamate system of rat liver. 685 46

Juvenile visceral steatosis (JVS) mouse is an animal model of human primary carnitine deficiency caused by a mutation of the gene encoding carnitine transporter, and suffers from various symptoms, such as fatty liver, growth retardation, hyperammonemia, hypoglycemia, and cardiac hypertrophy. We have shown that hyperammonemia during the weaning period (15-26 days of age) is caused by suppression of urea cycle enzyme gene expression. The suppression resulted from activation of a transcription factor, AP-1. We have found that a cis-element for AP-1 binding is present in the enhancer region of the carbamoylphosphate synthetase (CPS) gene, and that the AP-1 binding site is involved in the suppression of CPS induction by dexamethasone in cultured hepatocytes and in the suppression of CPS expression in the liver of JVS mice. The blood ammonia levels in JVS mice increased during the weaning period, and then decreased to almost control levels after 30 days of age. In this paper, we report that in adult JVS mice, ammonia levels again increased after starvation for at least 24 hr and this effect was suppressed by carnitine treatment. Starvation for 48 hr did not significantly suppress CPS activity in the liver and did not cause any change in hepatic ornithine concentration. The concentration of N-acetylglutamate in the liver of starved JVS mice was not significantly different from that of JVS mice treated with carnitine. These results indicate that the hyperammonemia in carnitine-deficient adult JVS mice during starvation and the suppression by carnitine treatment differ from those found during the weaning period, and thus the cause of hyperammonemia and the mechanism of suppression remain to be solved.
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PMID:Hyperammonemia in carnitine-deficient adult JVS mice used by starvation. 1260 12