226] Histidine decarboxylase (Lactobacillus 30a)

Abstract

Publisher Summary This chapter discusses the methods of preparation of Histidine Decarboxylase ( Lactobacillus 30a). Histidine decarboxylase has been isolated in crystalline form from Lactobacillus 30a, and its substrate specificity, mechanism of action, and subunit structure have been studied. Unlike most other amino acid decarboxylases so far studied, histidine decarboxylase does not involve pyridoxal phosphate in its action, but instead contains functional, covalently bound pyruvate residues. By conducting the decarboxylation of histidine in D 2 O, stereospecifically labeled histamine that contains deuterium on the α-carbon may be obtained. Histidine decarboxylase is specific for L -histidine and may be used for the determination of that amino acid. Histidine decarboxylase is noncompetitively inhibited by KCN and other carbonyl group reagents, and also by p-chloromercuribenzoate and other sulfhydryl reagents. Crystalline histidine decarboxylase does not contain significant amounts of pyridoxal phosphate, phosphorus, carbohydrate, or metal ions, and has the spectrum of a simple protein. Added pyridoxal phosphate does not increase its activity and is not involved in its action.