title: Purification and properties of threonine deaminase from the X-1 isolate of the genus Thermus.
abstract: Threonine deaminase (l-threonine dehydratase EC 4.2.1.16) has been partially purified from a new extreme thermophilic bacterium, Thermus X-1, which is similar to T. aquaticus YT-1. The threonine deaminase of strain X-1 has a maximal rate of reaction at 85 to 90 C and is more thermostable than the threonine deaminase from mesophilic bacteria. The enzyme has an apparent molecular weight of 100,000 to 115,000, a K(m) for l-threonine of 14 mM, a pH optimum of 8.0, and like other threonine deaminases also catalyzes the deamination of serine. However the Thermus X-1 threonine deaminase does not show a strong feedback inhibition by isoleucine. It is suggested that the regulation of the biosynthesis of isoleucine in this extreme theromophile may resemble that reported in Rodospirillum rubrum.
mesh_terms: D000096:Acetone; D000645:Ammonium Sulfate; D001419:Bacteria / Q000201:enzymology* / Q000254:growth & development; D002087:Butyrates / Q000096:biosynthesis; D002474:Cell-Free System; D011232:Chemical Precipitation; D002850:Chromatography, Gel; D004589:Electrophoresis, Disc; D006358:Hot Temperature; D006836:Hydro-Lyases / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007532:Isoleucine / Q000494:pharmacology; D008970:Molecular Weight; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D013053:Spectrophotometry; D013237:Stereoisomerism; D013912:Threonine / Q000378:metabolism
chemical_list: D002087:Butyrates; D007532:Isoleucine; D000096:Acetone; D013912:Threonine; D011732:Pyridoxal Phosphate; D006836:Hydro-Lyases; D000645:Ammonium Sulfate