Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.3.5.5 (CPS)
 1,262 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Total RNA or poly(A)(+) RNA of rat liver was translated in a rabbit reticulocyte or wheat germ protein-synthesizing system and the carbamyl phosphate synthetase I [carbamoyl-phosphate synthetase (ammonia); carbon dioxide: ammonia ligase (ADP-forming, carbamate-phosphorylating), EC 6.3.4.16] synthesized was isolated by indirect immunoprecipitation by using antibody purified on enzyme-bound Sepharose and Staphylococcus aureus cells. The in vitro product moved on sodium dodecyl sulfate/polyacrylamide gels as a polypeptide that was about 5000 daltons larger than the subunit of the mature enzyme (160,000 daltons). The same polypeptide was also obtained by direct immunoprecipitation or by a double-antibody precipitation method. The mature enzyme competed effectively with the in vitro product for interaction with anti-carbamyl phosphate synthetase I antibody. Digestion of the in vitro product by S. aureus protease gave a pattern of peptide fragments similar to that of the mature enzyme. A mitochondrial membrane preparation from rat liver converted the in vitro product into a polypeptide that comigrated with the mature subunit on sodium dodecyl sulfate gel electrophoresis. Similar proteolytic activity was not detected in either a cytosol or a microsomal fraction of rat liver. These results indicate that the enzyme is synthesized as a larger precursor which is converted to the mature form of enzyme by posttranslational processing.
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PMID:Cell-free synthesis and processing of a putative precursor for mitochondrial carbamyl phosphate synthetase I of rat liver. 22 76

1. A lag period of about 4 days preceded the onset of metamorphosis precociously induced by tri-iodothyronine in tadpoles of the giant American bullfrog (Rana catesbeiana). It was established by the accelerated synthesis or induction of carbamoyl phosphate synthetase and cytochrome oxidase in the liver, serum albumin and adult haemoglobin in the blood, acid phosphatase in the tail, and the increase in the hindleg/tail length ratio. 2. A 4- to 6-fold stimulation, 2 days after the induction of metamorphosis, of the rate of synthesis of rapidly labelled nuclear RNA in liver cells was followed by an increasing amount of RNA appearing in the cytoplasm. Most of the newly formed RNA on induction of metamorphosis was of the ribosomal type. An accelerated turnover at early stages of development preceded a net accumulation of RNA in the cytoplasm, with no change in the amount of DNA per liver. 3. Most hepatic ribosomes of the pre-metamorphic tadpoles were present as 78s monomers and 100s dimers; metamorphosis caused a shift towards larger polysomal aggregates with newly formed ribosomes that were relatively more tightly bound to membranes of the endoplasmic reticulum. 4. The appearance of new polyribosomes in the cytoplasm on induction of metamorphosis was co-ordinated in time with a stimulation of synthesis of phospholipids of the smooth and rough endoplasmic reticulum, followed by a gradual shift in preponderance from the smooth to the rough type of microsomal membranes. 5. Electron- and optical-microscopic examination of intact hepatocytes revealed a striking change in the distribution and nature of ribosomes and microsomal membranes during metamorphosis. 6. Ribosomes prepared from non-metamorphosing and metamorphosing animals were identical in their sedimentation coefficients and in the structural ribosomal proteins. The base composition and sedimentation coefficients of ribosomal RNA were also identical. Induction of metamorphosis also did not alter the incorporation of (32)P into the different phospholipid constituents of microsomal membranes. 7. Nascent (14)C-labelled protein with the highest specific activity was recovered in the ;heavy' rough membrane fraction of microsomes, whereas little (14)C was associated with ;free' polysomes. Protein synthesis in vivo was most markedly stimulated during metamorphosis in the tightly membrane-bound ribosomal fraction after the appearance of new ribosomes. 8. The rate of synthesis of macromolecules in vivo could not be followed beyond 7-8 days after induction because of variable shifts in precursor pools due to regression of larval tissues. 9. The stimulation of RNA and ribosome formation was specifically associated with the process of metamorphosis since no similar response to thyroid hormones occurred in those species (Axolotl and Necturus) in which the hormones failed to induce metamorphosis.
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PMID:The formation, distribution and function of ribosomes and microsomal membranes during induced amphibian metamorphosis. 558 18

A putative precursor of carbamoyl-phosphate synthase was isolated from a microsomal wash fraction and purified by high-pressure liquid chromatography. Autolytic degradation and limited proteolysis were used to characterize the putative precursor of carbamoyl-phosphate synthase and to show its similarity to the processed enzyme. The carbamoyl-phosphate synthase precursor underwent a time-dependent and concentration-dependent conversion into a dimeric or polymeric form. When labelled with 125I and incubated with foetal rat liver mitochondria the precursor was bound to the mitochondria and about 30% of the label was imported into the matrix space. This labelling required the presence of ATP and was time-dependent. Mitoplasts also imported the carbamoyl-phosphate synthase precursor. After import of the precursor, increases in carbamoyl-phosphate synthase activity could be demonstrated in foetal rat liver mitochondria.
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PMID:The import of carbamoyl-phosphate synthase into mitochondria from foetal rat liver. 711 41