Characteristics of the cysteinesulfinate-forming enzyme system in rat liver

Abstract

• 1.

  1. The oxidation of cysteine to cysteinesulfinate by rat-liver preparations in the presence of hydroxylamine has been studied. This compound is added to the assay system in order to inhibit the enzymatic destruction of the reaction product.

• 2.

  2. The optimum assay conditions for the enzyme system are reported.

• 3.

  3. The reaction is catalysed by a heat-labile factor found in the soluble fraction and is stimulated by TPNH, ferrous ions and mitochondria or microsomes. The stimulating activity in the particulate fractions is heat-labile.

• 4.

  4. The enzyme system appears to be specific for l-cysteine, as very little sulfinate formation was detected when d-cysteine, l-cystine, glutathione or cysteamine was used as substrate.

• 5.

  5. Among different rat tissues studied, only liver contained significant activity.

• 6.

  6. The enzyme system is inhibited by heavy-metal reagents (EDTA, cyanide, o-phenanthroline) and by the sulfhydryl reagents p-hydroxymercuribenzoate and iodoacetate, but not by arsenite.