The production of amines by bacteria

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Abstract
Of 14 strains of Escherichia coli tested, 12 decarboxylated l( + )arginine to form agmatine; 12 l( [long dash] )histidine to histamine; 13 /(+) lysine to cadaverine; 12 l( + )ornithine to putrescine and 9 l( + )glutamic acid to [gamma]-obutyric acid. The decarboxylases involved were active over a restricted range of pH, having optimal values of 4 in the cases of arginine, histidine and glutamic acid, of 4.5 for lysine and 5 for ornithine. The enzymes were very thermolabile at temps. above 20-25[degree] and organisms grown at 27[degree] were markedly more active than those grown at 37[degree]. At the optimum pH and 30[degree], the washed suspensions carried out a simple quantitative decarboxylation of the ammo-acids mentioned, producing the corr. amines which were isolated as their picrates and identified. To obtain active suspensions, the organisms were grown in a tryptic digest of casein with 2% glucose added. Substitution of glucose by other fermentable sugars showed that glucose has no specific effect on the production of the amino-acid decarboxylasea, but acts by providing a source of acid, the controlling factor being the pH of the growth medium; bacteria grown at pH 5 in a non-carbohydrate medium having higher activities than those grown in a similar medium containing glucose. In all cases, organisms grown at pH 7 in non-carbohydrate media had little decarboxylase activity and this activity was greatly increased (20-100 X) by growing the organism at pH 5.

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