Histidine Decarboxylase of Rat Stomach and Other Mammalian Tissues

Abstract

With minute quantities of C¹⁴ l-histidine as substrate, rat stomach histidine decarboxylase shows a far higher activity than that from any other mammalian organ tested. Its maximum activity is ph 7.2. The maximum activity of rabbit kidney histidine decarboxylase is 8.0. Although the activity of the latter is greatly enhanced by benzene, rat stomach histidine decarboxylase activity is strongly inhibited by benzene. It is concluded that there are at least two mammalian enzymes with the same specificity which have major differences in molecular configuration. Studies of some properties of histidine decarboxylase are presented. Histidine decarboxylase activity of rat stomach drops markedly as early as 1 day following hypophysectomy. No comparable drop follows adrenalectomy.