Effects of cations on amino acid decarboxylases

Abstract

The activity of 7 amino acid decarboxylases in Escherlchia coli and Clostridium welchii acting upon L-lysine, L-arginine, L-ornithine and L-glutamate was increased (up to about 45%) by some or all of the bivalent cations Mg++, Mn++, Co++, Ca++, Ba++, Ni++ and Fe++. The activation with Mg++ ions was greater in the presence than in the absence of pyridoxal phosphate. A histidine decarboxylase of E. coli F was stimulated by pyridoxal phosphate but not by any of the 9 metal ions tested. Ethylene diaminetetraacetate had only a small inhibitory effect, which was reversed by addition of Mg++ ions. With the same group of enzymes, K+, Li and NH4+ ions had little or no effect and, except with lysine decarboxylase of E. coli 8571, the tervalent ions Fe+++ and Al+++ were inhibitory. The L-glutamic acid decarboxylases of vegetable marrow, orange fruit or rat brains were not stimulated by cations nor inhibited by ethylene diaminetetraacetic acid. The re-sults are discussed in relation to the hypothesis of Metzler et al (1954).