Induced formation of leucine decarboxylase in Proteus vulgaris

Abstract

Proteus vulgaris possesses an inducible leucine decarboxylase. The formation of this enzyme was dependent on a source of carbon and energy in addition to an inducer, and was more rapid and extensive in growing cultures than in dense, washed suspensions. A variety of compounds structurally related to leucine were tested for their ability to combine with the enzyme (acting as substrates or inhibitors) and to induce its formation. All the known substrates were inducers. isoValerate and isobutylamine, which inhibited the enzyme, could not induce its formation, whereas alanine was an inducer but was inert in the enzyme system. Those amino acids which were both substrates and inducers of the enzyme showed an affinity for the induction system at least 10 times as great as their affinity for the enzyme. The induction system closely resembles the enzyme system but is distinct from it. This is in keeping with the theory that inducers combine with a bound form of the enzyme.