Portal de Periódicos da CAPES

Cystathionine γ-synthesis from homocysteine and cysteine by mammalian tissue

1974; Academic Press; Volume: 9; Issue: 1 Linguagem: Inglês

10.1016/0006-2944(74)90087-8

1557-7996

Harris H. Tallan, John A. Sturman, Theresa A. Pascal, Gerald E. Gaull,

Neonatal Health and Biochemistry

Abstract Extracts of human and of rat liver synthesize [ 35 S]cystathionine from homocysteine and [ 35 S]cysteine, the reaction thus taking place by γ-activation of the homocysteine and addition of cysteine. Optimum conditions for the synthesis were established; human liver and rat liver differ in their requirement for cysteine and in pH optimum. Upon fractionation of crude extracts with ammonium sulfate, homocysteine cystathionine-γ-synthase activity paralleled that of cystathionase, with both human and rat liver. In each case the two activities were precipitated by homologous monospecific rabbit anti-cystathionase serum, confirming that the γ-synthase activity is a function of cystathionase. Administration of homocysteine and [ 35 S]cysteine to mice resulted in the production of [ 35 S]cystathionine in liver, kidney, and brain. However, evidence in the literature and unpublished results from this laboratory indicate that administration of cysteine to patients with homocystinuria, who presumably have elevated endogenous tissue concentrations of homocysteine, does not lead to the production of cystathionine, and it is speculated that in man there may be a control mechanism to prevent γ-activation of homocysteine.