TsISTATIONYN — R-amino-R-karb-oksietil-gomotsistein, diamino-di-carboxylic sulfur-containing amino acid; is the mixed monothioester, representing the S-replaced cysteine. C. — one of the important metabolites which are formed in the course of transfer of sulfur from methionine (see) on cysteine (see). Genetically caused disturbances of exchange of C. at the person are the reason of hereditary diseases — tsistationinuriya (see) and homocystinurias (see).
C. has 4 optically active diasta to a reoizoma ra: L-tsistationin,
L - hallo-tsistationin, D - oilo-cyst-thionine and „iyezo-tsistationin.
L-tsistationin (1 g in 100 ml 1 N salt to - you) at 20 ° has specific rotation of the plane of the polarized light of [a]2^ = + 23,7 °; * °pl this isomer of a tsistationin 312 ° (with decomposition).
In a human body the C especially is a lot of. it is found in tissue of a brain. The C is formed. in the course of Peresuljfidirovaniya (see) between O-suktsinilgomoserinom and cysteine catalyzed by piridoksalfos-fatzavisimy enzyme tsistatio-nin-at-synthase (KF 184.108.40.206) at metabolism of methionine or in the course of formation of cysteine in reaction of L-gomotsisteina with L-serine (see Serine) catalyzed tsistationin-by R-synthase (KF 220.127.116.11). Splitting of C. it is provided with cyst-thionine-at-lyase (KF 18.104.22.168). In the specified reactions of C. is a metabolite. Suppression by cystine (see) synthesis tsistationin-| 3 synthases in a liver slows down transformation of gomo-cysteine in tsistationin. Genetically caused metabolic block of this reaction called by defect fe a rment tsistationin-r-sin gases
leads to a serious hereditary illness — a homocystinuria, characterized by defeat of connecting fabric, nervous, bone, muscular and cardiovascular systems.
Bibliography: At and y t And. and d river. Fundamentals of biochemistry, the lane with English, t. 1 — 3, M., 1981.
A. M. Shaposhnikov.