Main Content

The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 3616

Johan A. Hellebust and Jacques Larochelle; Compartmentation and Activities of Enzymes Involved in the Metabolism of Amino Acids Implicated in Osmoregulatory Mechanisms in Acanthamoeba castellanii. J.Protozool. 35(4):498-502, 1988

Reprint

In File

Notes

Glutamate dehydrogenase in Acanthamoeba castellanii is an NAD-dependent cytosolic enzyme. This is similar to glutamate dehydrogenases in Phycomycetes, but very different from the dual coenzyme-specific enzymes located in mitochondria in animals and in mitochondria and chloroplasts in higher plants. Pyrroline-5-carboxylate (P-5-C) reductase occurs also in the cytoplasm in A. castellanii and has very affinities for L-P-5-C (Km=12 µM) and NADH (Km=15 µM). In contrast, ornithine aminotransferase and proline oxidase are mitochondrial enzymes. No proline-inhibited gamma-glutamyl kinase was detected while an active glutamine synthetase was found in the cytosolic compartment. Evidence for a mitochondrial transport system for L-proline was obtained. Two possible pathways for proline biosynthesis in A. castellanii are discussed based on information obtained about activities and subcellular compartmentation of enzymes.