Carbamyl phosphate synthetase in the chick

1969 ◽  
Vol 47 (1) ◽  
pp. 61-63 ◽  
Author(s):  
Charles G. Maresh ◽  
Theodore H. Kwan ◽  
Sumner M. Kalman
Keyword(s):  
Enzyme Activity ◽  
Chick Embryo ◽  
Urea Cycle ◽  
Mitochondrial Fraction ◽  
Pyrimidine Biosynthesis ◽  
Developmental Pattern ◽  
Synthetase Activity ◽  
Young Chick ◽  
Carbamyl Phosphate ◽  
Carbamyl Phosphate Synthetase

Carbamyl phosphate synthetase activity is present in the liver of the chick embryo and in the young chick. This enzyme activity is not dependent upon acetylglutamate and is not present in the mitochondrial fraction. Because the urea cycle is not present in chick liver and because of the developmental pattern of the enzyme activity, we infer that this enzyme is involved in pyrimidine biosynthesis.

scholarly journals N-Acetylglutamate and its changing role through evolution

2003 ◽  
Vol 372 (2) ◽  
pp. 279-290 ◽  
Author(s):  
Ljubica CALDOVIC ◽  
Mendel TUCHMAN
Keyword(s):  
Amino Acid ◽  
Autosomal Recessive ◽  
Urea Cycle ◽  
Evolutionary Relationship ◽  
Autosomal Recessive Disorder ◽  
The Other ◽  
Arginine Biosynthesis ◽  
Carbamyl Phosphate ◽  
Carbamyl Phosphate Synthetase ◽  
Changing Role

N-Acetylglutamate (NAG) fulfils distinct biological roles in lower and higher organisms. In prokaryotes, lower eukaryotes and plants it is the first intermediate in the biosynthesis of arginine, whereas in ureotelic (excreting nitrogen mostly in the form of urea) vertebrates, it is an essential allosteric cofactor for carbamyl phosphate synthetase I (CPSI), the first enzyme of the urea cycle. The pathway that leads from glutamate to arginine in lower organisms employs eight steps, starting with the acetylation of glutamate to form NAG. In these species, NAG can be produced by two enzymic reactions: one catalysed by NAG synthase (NAGS) and the other by ornithine acetyltransferase (OAT). In ureotelic species, NAG is produced exclusively by NAGS. In lower organisms, NAGS is feedback-inhibited by l-arginine, whereas mammalian NAGS activity is significantly enhanced by this amino acid. The NAGS genes of bacteria, fungi and mammals are more diverse than other arginine-biosynthesis and urea-cycle genes. The evolutionary relationship between the distinctly different roles of NAG and its metabolism in lower and higher organisms remains to be determined. In humans, inherited NAGS deficiency is an autosomal recessive disorder causing hyperammonaemia and a phenotype similar to CPSI deficiency. Several mutations have been recently identified in the NAGS genes of families affected with this disorder.

Inhibition of urea cycle enzymes by aspartic acid analogues

1969 ◽  
Vol 47 (3) ◽  
pp. 361-369
Author(s):  
S. M. Bayer ◽  
W. C. McMurray
Keyword(s):  
Aspartic Acid ◽  
Energy Production ◽  
Urea Cycle ◽  
Argininosuccinate Synthetase ◽  
Substrate Type ◽  
Carbamyl Phosphate ◽  
Enzyme Preparations ◽  
Carbamyl Phosphate Synthetase ◽  
Liver Homogenates

The inhibition of urea biosynthesis by analogues of aspartic acid was studied in vitro in homogenates and enzyme preparations from rat liver. Each of the analogues tested inhibited the overall utilization of citrulline for urea formation by liver homogenates. The concentrations required to give 50% inhibition were: N-allylaspartate, 0.248 M; α-methylaspartate, 0.140 M; β-methylaspartate, 0.078 M; and β-hydroxy-β-methylaspartate, 0.038 M. The β-substituted analogues partly replaced aspartate as a substrate for citrulline utilization in liver homogenates. The replacement was probably due to transamination of the analogues with oxaloacetate, since the effect was not observed when the assay mixture did not contain a substrate which could yield oxaloacetate.A study of individual enzymes of the urea cycle showed that arginase, argininosuccinase, and ornithine transcarbamylase were not greatly affected by the analogues. However, carbamyl phosphate synthetase as well as argininosuccinate synthetase were strongly inhibited, suggesting that the analogues act by some mechanism other than simple antagonism of aspartate. Part of the inhibition was related to the ability of the analogues to complex Mg2+, since increased concentrations of Mg2+ prevented the inhibition of carbamyl phosphate synthetase and reduced the inhibition of argininosuccinate synthetase by α-methylaspartate and N-allylaspartate. In addition, β-methylaspartate was found to depress oxidative and phosphorylative reactions, thus interfering with the energy production required for urea formation.Aspartic acid in concentrations comparable with those required to effect inhibition by α-methylaspartate produced a marked inhibition of citrulline utilization in liver homogenates and of purified argininosuccinate synthetase. This observation suggests that part of the inhibitions observed with the analogues are of the "substrate type".

The Role of Thyroid Hormone in the Regulation of Hepatic Carbamyl Phosphate Synthetase Activity inRana catesbeiana*

Endocrinology ◽  
1991 ◽  
Vol 129 (5) ◽  
pp. 2298-2304 ◽  
Author(s):  
VALERIE ANNE GALTON ◽  
CHRISTINE M. MORGANELLI ◽  
MARK J. SCHNEIDER ◽  
KAREN YEE
Keyword(s):  
Thyroid Hormone ◽  
Synthetase Activity ◽  
Carbamyl Phosphate ◽  
Carbamyl Phosphate Synthetase

scholarly journals Detection and location of the enzymes of de novo pyrimidine biosynthesis in mammalian spermatozoa

Reproduction ◽  
2002 ◽  
pp. 757-768 ◽  
Author(s):  
EA Carrey ◽  
C Dietz ◽  
DM Glubb ◽  
M Loffler ◽  
JM Lucocq ◽  
...  
Keyword(s):  
De Novo ◽  
Pyrimidine Biosynthesis ◽  
Dihydroorotate Dehydrogenase ◽  
Aspartate Transcarbamylase ◽  
Carbamyl Phosphate ◽  
Pyrimidine Nucleotides ◽  
Carbamyl Phosphate Synthetase ◽  
De Novo Biosynthesis ◽  
Ump Synthase ◽  
Mammalian Spermatozoa

Enzymes of the pathway for de novo biosynthesis of pyrimidine nucleotides have been reported in spermatozoa from fruitfly and mammals. The aim of the present study was to test the hypothesis that the enzymes for biosynthesis of uridine monophosphate (UMP) are concentrated near the mitochondria, which are segregated in the mid-piece of spermatozoa. Baby hamster kidney fibroblasts were compared with spermatozoa from rams, boars, bulls and men. Antibodies raised against synthetic peptides from sequences of the multienzyme polypeptides containing glutamine-dependent carbamyl phosphate synthetase, aspartate transcarbamylase and dihydroorotase (CAD) and UMP synthase, which catalyse reactions 1-3 and 5-6, respectively, were used, together with an affinity-purified antibody raised against dihydroorotate dehydrogenase (DHODH), the mitochondrial enzyme for step 4. Western blot analysis, immunofluorescent microscopy and immunoelectron microscopy confirmed that CAD and UMP synthase are found in the cytoplasm around and outside the mitochondria; DHODH is found exclusively inside the mitochondria. CAD was also located in the nucleus, where it has been reported in the nuclear matrix, and in the cytoplasm, apparently associated with the cytoskeleton. It is possible that CAD in the cytoplasm has a role unconnected with pyrimidine biosynthesis.

VARIATION WITH AGE OF THE ENZYMES OF THE UREA CYCLE AND ASPARTATE TRANSCARBAMYLASE IN RAT LIVER

1967 ◽  
Vol 45 (9) ◽  
pp. 1427-1432 ◽  
Author(s):  
R. Charbonneau ◽  
A. Roberge ◽  
L. Berlinguet
Keyword(s):  
Urea Cycle ◽  
Protein Biosynthesis ◽  
Adult Life ◽  
Limiting Factor ◽  
Argininosuccinate Synthetase ◽  
Aspartate Transcarbamylase ◽  
Carbamyl Phosphate ◽  
Carbamyl Phosphate Synthetase ◽  
Metabolic Activities ◽  
Very High

The activities of aspartate transcarbamylase and of five enzymes involved in the urea cycle were determined in the liver of rats from the embryonic state to adulthood. Aspartate transcarbamylase activity is very high in the embryo and at birth. It remains high until the rat reaches a body weight of 50 g, after which there is a rapid decrease which levels off to a plateau at adulthood. The enzymatic activities of carbamyl phosphate synthetase, ornithine transcarbamylase, argininosuccinate synthetase, argininosuccinase, and arginase are very low at the embryonic stage. The activity of these enzymes increases gradually with age until a plateau is reached, except for argininosuccinase which also increases in young animals but decreases in adult life. Of these enzymes, argininosuccinate synthetase always has the lowest activity and seems to be the limiting factor in the synthesis of urea. These results indicate that the biosynthesis of pyrimidines and urea vary inversely at different ages that correspond to different metabolic activities of the animals. Thus, an inverse relation is established between the two pathways from carbamyl phosphate, leading to protein biosynthesis (formation of RNA from orotic acid) and to protein catabolism (formation of urea).

scholarly journals Neonatal hyperammonaemia with complete absence of liver carbamyl phosphate synthetase activity.

1978 ◽  
Vol 53 (3) ◽  
pp. 230-234 ◽  
Author(s):  
S Mantagos ◽  
S Tsagaraki ◽  
E A Burgess ◽  
V Oberholzer ◽  
T Palmer ◽  
...  
Keyword(s):  
Synthetase Activity ◽  
Carbamyl Phosphate ◽  
Carbamyl Phosphate Synthetase
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