Anticatalase Activity « in vitro » and « in vivo » of Cysteine, Tyrosine and Some Related Compounds, and its Significance for the Anticatalase Activity of Tumors.

Abstract

Like cysteine and some of its derivatives, tyrosine inhibits liver catalase not only « in vitro » but also « in vivo ». Among the analogues of tyrosine tested, dihydroxyphenylalanine and dihydroxyphenethylamine possess « in vitro » the same activity as tyrosine; the activity of p-hydroxyphenylethanolamine is lower; phenylalanine is inactive. The «in vitro» activity seems to be directly correlated with the auto-oxidability of the various compounds. None of the analogues of tyrosine tested was active «in vivo». The depressing activity of cysteine and of tyrosine on liver catalase apparently has no relationship with the similar action of tumors.