The Effect of Some Cystine Derivatives on Catalase Activity^*

Cysteine, cysteine sulfinic acid, 2-amino-ethane sulfinic acid, and sodium sulfite-cystine disulfoxide reaction products are all good inhibitors of catalase in vitro. They and cystine disulfoxide also lower rat liver catalase activity in vivo, with 2-amino-ethane sulfinic acid showing only a weak activity. Only cysteine, of the above compounds, affects the absorption spectrum of catalase. Iodoacetate reverses the catalase-inhibiting action of cysteine, and of cystine disulfoxide-sodium sulfite reaction products, but not of cysteine sulfinic acid and of tumor “Kochsafts.” Formal reverses the catalase-inhibiting action of all the above. Changes in the absorption spectrum of catalase are effected only by cysteine and “Kochsaft” material.