The toxicity of 2-mercaptoethylamine to Saccharomyces carlsbergensis and its reversal

Abstract

2-Mercaptoethylamine (cysteamine, 2-aminoethanethiol) inhibited the growth of Saccharomyces carlsbergensis (A.T.C.C. 4228); the toxicity was found to be alleviated by a variety of compounds, such as β-alanine and its related compounds, dl-penicillamine, the intermediates of the tricarboxylic acid cycle and their related compounds, malonic acid, dl-thioctic acid, kojic acid, soybean phospholipides, orthophosphoric acid, organic phosphates, and inorganic salts. The degree of growth inhibition by 2-mercaptoethylamine also decreased as the pH of the assay medium changed from 5.5 to 3.0. The results have been interpreted to mean: ( a) 2-Mercaptoethylamine forms a complex with a metallic ion (especially a bivalent one) which is essential for the growth of S. carlsbergensis, thus causing growth inhibition. ( b) As the pH of the medium decreases, the fraction of a metal ion bound with 2-mercaptoethylamine also diminishes, thus causing poor growth inhibition, ( c) A type of reversing agent competes with 2-mercaptoethyl-amine for a metal, and the complex thus formed with the former is able to donate the metal for the growth of the organism. Results showed that such competition can take place solely in vitro. ( d) Another type of reversing agent saturates the active sites in 2-mercaptoethylamine and thus the mercapto compound can no longer function as an inhibitor.