D-citrulline

Figure 12.4-13. Production of D-citrulline from L-ornithine by means of Agrobacterium radiobacter.

Likely impurities are citrulline, arginine and D-omithine. Crystd from water by adding 4 volumes of EtOH and dried in a vacuum desiccator over fused CaCl2. 

QH,4N402 74-79-3) see Arginine aspartate Arginine pidolate Cetrorelix l arginine monohydrochloride (QH15CIN4O2 1119-34-2) see Citrulline D-Arg(Tos)-Gly-OEt... 

In view of the toxicity of ammonia, complete absence of any one of the enzymes of the cycle is fatal. Nonetheless, disorders of the cycle do occur, which are caused by a low activity of one of the enzymes or carbamoyl phosphate synthetase. In addition, defects in N-acetylglutamate synthase have been reported, but they are very rare. With the exception of ornithine transcarbamoylase, the deficiencies have an autosomal recessive mode of inheritance. The transcarbamoylase deficiency is inherited as an X-linked dominant trait, usually lethal in male patients. A deficiency of carbamoyl phosphate synthetase, ornithine transcarbamoylase or argininosuccinate synthetase results in accumulation and excretion of citrulline. A deficiency of argininosuccinate lyase results in the accumulation and excretion of argininosuccinate and arginine (Table 10.5). The abbreviations CPSD, OTCD, ASD, ALD and AD stand, respectively, for the deficiencies of these enzymes, where D stands for deficiency. 

Renaud, J. P., Boucher, J. L., Vadon, S., Delaforge, M., and Mansuy, D. (1993). Particular ability of liver P450s3A to catalyze the oxidation of N omega-hydroxyarginine to citrulline and nitrogen oxides and occurrence in no synthases of a sequence very similar to the heme-binding sequence in P450s. Biochem. Biophys. Res. Commun. 192, 53-60. 

S-Citrulline (2-amino-5-ureidopentanoic acid) [2436-90-0] M 175.2, m 222°, [a] D +24.2° (in 5M HC1). Likely impurities are arginine, and ornithine. Crystd from water by adding 5 volumes of EtOH. Also crystd from water by addn of MeOH. 

Absolute Configuration of Citrulline The citrulline isolated from watermelons has the structure shown below. Is it a d- or L-amino acid Explain. 

Correct answer = D. Methionine is the precursor of cysteine. An increase in gluconeogenesis releases increased ammonia and results in increased urea production. The essential amino acids leucine and lysine are ketogenic. Ornithine and citrulline are amino acids that are intermediates in the urea cycle, but are not found in tissue proteins. 

Briand, J., Blehaut, H., Calvayrac, R., Laval-Martin, D. Use of a microbial model for the determination of drug effects on cell metabolism and energetics study of citrulline-malate. Biopharm. Drug Dispos. 1992,13 1-22. 

As a congenital disorder, an enzyme deficiency in the urea cycle relates to carbamoylphosphate synthetase or N-ace-tyl-glutamate synthetase (= hyperammonaemia type I) and ornithine carbamoyltransferase (= hyperammonaemia type II) (D.B. Flannery et al., 1982). (27) (s. p. 594) This condition mainly affects the channelling of ammonium into the mitochondria and the conversion of ornithine into citrulline. (s. fig. 3.12) Similar acquired enzymopathies can be expected in Reye s syndrome and in cases of zinc deficiency. Such a hyperammonaemia syndrome can also produce the clinical picture of HE. 

Unlike fractions of pig-kidney protein, Neurospora crassa extracts can use L-glutamine, but not ammonium salts nor ammonium salts plus adeno-sine-5-triphosphoric acid. No synthesis of D-glucosamine is stimulated in Neurospora extracts by L-glutamic acid, L-aspartic acid, L-asparagine, L-alanine, glycine, L-valine, L-leucine, L-lysine, L-arginine, L-serine, L-cys-teine, L-citrulline, L-ornithine, butyramide, putrescine, or urea. Recently, a protein fraction has been discovered, in rat liver, that converts D-glucose... 

D) ornithine directly reacts with carbamoyl phosphate to form citrulline... 

The carbamoyl phosphate, which functions as an activated carbamoyl group donor, now enters the urea cycle. The cycle has four enzymatic steps. First, carbamoyl phosphate donates its carbamoyl group to ornithine to form citrulline, with the release of P, (Fig. 18-10, step (D) Ornithine plays a role resembling that of oxaloacetate in the citric acid cycle, accepting material at each turn of the cycle. The reaction is catalyzed by ornithine transcarbamoylase, and the citrulline passes from the mitochondrion to the cytosol. 

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