title: Cysteine metabolism in the cestode Hymenolepis diminuta.
abstract: The major pathways for cysteine catabolism in Hymenolepis diminuta have been investigated. The parasite has an active cystathionine-beta-synthase and, as in other tissues, this enzyme has a wide substrate specificity. However, the enzyme from H. diminuta differs significantly from the mammalian enzyme in showing a high serine sulphydrase activity and a high serine lyase activity. There was only low gamma-cystathionase activity in H. diminuta and again the enzyme showed a range of substrate specificities. Cysteine aminotransferase activity was readily demonstrated in the tapeworm, but there was no evidence for 3-mercaptopyruvate sulphotransferase activity. An oxidative pathway for cysteine catabolism in H. diminuta was shown by the presence of cysteine dioxygenase and cysteine sulphinate transaminase. The properties of the helminth cysteine dioxygenase were very similar to those of rat liver. H. diminuta was able to reduce cystine to cysteine via a glutathione-cysteine transhydrogenase system.
authors.affiliation: Departamento de Parasitologia, Facultad de Farmacia, Universidad de Salamanca, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Gomez-Bautista
authors.forename: J
authors.initials: J
authors.lastname: Barrett
mesh_terms: D000818:Animals; D003541:Cystathionine beta-Synthase / Q000378:metabolism; D003542:Cystathionine gamma-Lyase / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism*; D050558:Cysteine Dioxygenase; D049308:Dioxygenases; D006926:Hymenolepis / Q000201:enzymology* / Q000378:metabolism; D008099:Liver / Q000201:enzymology; D008297:Male; D010105:Oxygenases / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity; D000637:Transaminases / Q000378:metabolism
chemical_list: D010105:Oxygenases; D049308:Dioxygenases; D050558:Cysteine Dioxygenase; D000637:Transaminases; C019973:cysteine sulfinate transaminase; C019968:cysteine aminotransferase; D003541:Cystathionine beta-Synthase; D003542:Cystathionine gamma-Lyase; D003545:Cysteine