Selenocysteine lyase, a novel enzyme that specifically acts on selenocysteine. Mammalian distribution and purification and properties of pig liver enzyme.
We have found a novel enzyme that exclusively decomposes L-selenocysteine into L-alanine and H2Se in various mammalian tissues, and have named it selenocysteine lyase. The enzyme from pig liver has been purified to homogeneity. It has a molecular weight of approximately 85,000, and contains pyridoxal 5'-phosphate as a coenzyme. Its maximum reactivity is at about pH 9.0. Balance studies showed that 1 mol of selenocysteine is converted to equimolar amounts of alanine and H2Se. The following amino acids are insert: L-cysteine, L-serine, L-cysteine sulfinate, selenocysteamine, Se-ethyl-DL-selenocysteine, and L-selenohomocysteine. L-Cysteine (Ki, 1.0 mM) competes with L-selenocysteine (Km, 0.83 mM) to inhibit the enzyme reaction. The enzyme is the first proven enzyme that specifically acts on selenium compounds.
D000818:Animals; D003545:Cysteine / Q000031:analogs & derivatives / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008190:Lyases / Q000378:metabolism*; D008970:Molecular Weight; D012643:Selenium / Q000378:metabolism; D017279:Selenocysteine; D013045:Species Specificity; D013053:Spectrophotometry; D013379:Substrate Specificity; D013552:Swine; D014018:Tissue Distribution
D017279:Selenocysteine; D008190:Lyases; C034278:selenocysteine lyase; D012643:Selenium; D003545:Cysteine