From Big Medical Encyclopedia

TsITRULLYN (synonym: N-5-karb-

amoilornitin, about-ureidonorvalin) — and - amino-5-ureidovalerianic acid, or 2-amino-5-ureidovaleria-new acid, amino acid, the metabolite which is formed in the course of biosynthesis of the major end product of a nitrogen metabolism — urea and arginine; genetically caused disturbance of synthesis of citrulline is the reason of a serious hereditary illness. At plants of C. participates in nitrogen fixation. In the nature H2NCONH(CH2)3CH(NH2)COOH citrulline meets in the form of L-and D-isomers (see the Isomerism). Proteins citrulline is not included, but at their hydrolysis can be formed of arginine (see).

In a free look L-citrulline contains in juice of a water-melon (in it C. it was found for the first time in 1914 and received the name from armor. names of a water-melon Citrullis vulgaris), and also in juice and fabrics of other plants. C. it is found also in microorganisms. C are rich. root nodules bean, used as a source for receiving this amino acid. C. contains in tissues of animals and the person. Content of L-citrulline in a blood plasma of the person averages 0,6 mg! 100 ml, contain in cerebrospinal liquid traces of C., in milk and urine C. usually do not find. From urine of healthy children and adults the gomotsitrul-lean of NH2CONH(CH2)4CH(NH2)COOH is allocated, excretion to-rogo at children is higher, than at adults.

Pier. the weight (weight) of citrulline is equal to 175,19; D-and L-isomers of citrulline crystallize in the form of needles from ethanol mixture with water, rastvorima in water, L-citrulline not rastvortag in ethanol and methanol, its £пл 222 — 234 ° (with decomposition), [oc]D from +3,4 to +3,7 ° (in water). With ninhydrin (see). C. gives red-violet coloring, this staining reaction is used for its definition (see Amino acids, definition of amino acids). From the concentrated solutions citrulline is besieged phosphatomolybdic to - that. In the concentrated alkali C. turns into ornithine (see). C. it is formed at hydrolysis of arginine by means of barium hydroxide of Wa (IT) 2. In the preparative number of C. receive from copper


of a complex of ornithine, copper oxide and urea (see).

L-citrulline in a cycle of urea is formed at condensation of a karb-amoilfosfat and ornithine in the reaction catalyzed mitochondrial ornithine-karbamoiltransferazoy (KF In cytosol under the influence of an argininosuktsinat-sintetaza (KF citrulline is condensed with aspartic acid (see) with education argininyantar-ache to - you are (argininosuktsinata), edges then it is split on arginine — the direct predecessor of urea — and fumaric to - that. In live organisms of C. can be exposed to transamination with education £-keto-5-karbamidovale-rianovoy to - you. With the participation of enzyme citrullineelements (KF citrulline is decarboxylized and deaminized with formation of ornithine.

At nek-ry microorganisms (clostridiums. streptococci and mycoplasmas) L-citrulline is formed as an intermediate product at fermentation of L-arginine to L-ornithine; during the splitting of C. ornithine and karbamoil-phosphate — the donor of makroergichesky phosphatic group for phosphorylation of ADF with formation of ATP is formed. A number of microorganisms carries out disintegration of arginine with formation of C. and ammonia with the participation of enzyme of an argininedeiminase (KF

Genetically caused insufficiency of specific isoenzymes of an argininosuktsinat-sintetaza is the reason of a serious hereditary illness — tsitrul-linuriya, at Krom accumulation of L-citrulline in blood is observed. C. in high concentration is not exposed to a reabsorption in kidneys, and in days with urine at the sick person several grams of C are constantly removed. At a tsitrullinuriya also raised excretion of a lysine, arginine, cystine and ornithine and sharp increase in content of ammonia in blood can be observed (see Aminoatsiduriya). Clinically the disease is shown by a delay of mental development, attacks of vomiting.

Tsitrullinuriya is diagnosed on the basis of data of the kliniko-genetic analysis, at Krom biochemical researches have crucial importance (the qualitative and quantitative content of amino acids in blood and urine, concentration of ammonia in blood serum).

Treatment of a tsitrullinuriya, as well as other hereditary diseases (see), has pathogenetic character.

Bibliography: L e N and N d A. Biot's ER

chemistry, the lane with English, page 82, etc., M., 1976; M ei s te of A. Biochemistry of the amino acids, v. 1—2, N. Y. — L., 1965. See also bibliogr. to St. Amino acids.

N. V. Gulyaeva.