title: Characterization of the enzymic capacity for cysteine desulphhydration in liver and kidney of the rat.
abstract: The contribution of cystathionine gamma-lyase, cystathionine beta-synthase and cysteine aminotransferase coupled to 3-mercaptopyruvate sulphurtransferase to cysteine desulphhydration in rat liver and kidney was assessed with four different assay systems. Cystathionine gamma-lyase and cystathionine beta-synthase were active when homogenates were incubated with 280 mM-L-cysteine and 3 mM-pyridoxal 5'-phosphate at pH 7.8. Cysteine aminotransferase in combination with 3-mercaptopyruvate sulphurtransferase catalysed essentially all of the H2S production from cysteine at pH 9.7 with 160 mM-L-cysteine, 2 mM-pyridoxal 5'-phosphate, 3 mM-2-oxoglutarate and 3 mM-dithiothreitol. At more-physiological concentrations of cysteine (2 mM) cystathionine gamma-lyase and cystathionine beta-synthase both appeared to be active in cysteine desulphhydration, whereas the aminotransferase pathway did not. The effect of inhibition of cystathionine gamma-lyase by a suicide inactivator, propargylglycine, in the intact rat was also investigated; there was no significant effect of propargylglycine administration on the urinary excretion of total 35S, 35SO4(2-) or [35S]taurine formed from labelled dietary cysteine.
mesh_terms: D000480:Alkynes / Q000494:pharmacology; D000818:Animals; D003541:Cystathionine beta-Synthase / Q000378:metabolism; D003542:Cystathionine gamma-Lyase / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism*; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006862:Hydrogen Sulfide / Q000378:metabolism; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects / Q000201:enzymology*; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution; D000637:Transaminases / Q000378:metabolism
chemical_list: D000480:Alkynes; C009055:propargylglycine; D000637:Transaminases; C019968:cysteine aminotransferase; D003541:Cystathionine beta-Synthase; D003542:Cystathionine gamma-Lyase; D003545:Cysteine; D005998:Glycine; D006862:Hydrogen Sulfide