L-Glutamate-l-carboxylase in Intestinal Parasites

Abstract

GLUTAMATE decarboxylase, an enzyme widely found in animals, plants and micro-organisms, has been searched for in intestinal parasites. We have found activity in the four species examined: Ascaridia galli, Ascaris lumbricoides, Taenia solium and Moniezia expansa. Cavier and Savel¹ discovered several amino-acid decarboxylases in Ascaris lumbricoides but glutamate decarboxylase was not reported. Campbell² identified 4-aminobutyrate, product of the reaction, in the free amino-acid fraction of several cestodes, and Monteoliva³ found it in the whole homogenate of Ascaridia galli. The direct relation of 4-aminobutyrate with the tricarboxylic acid cycle—through transamination with 2-oxoglutarate–has been found in brain⁴, in micro-organisms⁵ and in plant seeds and tubers⁶. Impaired respiration mutants of Saccharomyces cerevisiae show increased activity while in normal yeast strains glutamate decarboxylase activity increases as oxygen supply decreases⁷. As in Ascaris⁸, succinic acid accumulates in both cases⁹. The metabolism of intestinal parasites being predominantly anaerobic¹⁰, the investigation of a Krebs cycle by-pass system seems worth while.