Biomaterial Database

Effects of amino acids on Thiobacillus acidophilus. II. Threonine deaminase. 1980

G Proteau, and M Silver

Biosynthetic L-threonine deaminase was partially purified 73-fold with a 60% recovery from Thiobacillus acidophilus by ammonium sulfate fractionation and by Sepharose 6B-C1 chromatography. The optimal pH for enzyme activity was between 9.0 and 10.0 and no optimal pH shift was observed in the presence of L-isoleucine, an inhibitor. The enzyme was effectively inhibited by L-isoleucine and showed homotropic interaction only in the presence of L-isoleucine. Kinetic studies indicate that there are at least two threonine binding sites and at least two isoleucine binding sites. The Km for threonine is 2.5 x 10(-3) M. The inhibition due to isoleucine is reversed by low concentrations of L-valine. L-Valine at high concentration acts as a substrate analogue and competitively inhibits L-threonine binding at the active site; the K1 is 1.6 x 10(-2) M.

UI	MeSH Term	Description	Entries
D007532	Isoleucine	An essential branched-chain aliphatic amino acid found in many proteins. It is an isomer of LEUCINE. It is important in hemoglobin synthesis and regulation of blood sugar and energy levels.	Alloisoleucine,Isoleucine, L-Isomer,L-Isoleucine,Isoleucine, L Isomer,L-Isomer Isoleucine
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D013237	Stereoisomerism	The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)	Molecular Stereochemistry,Stereoisomers,Stereochemistry, Molecular,Stereoisomer
D013855	Thiobacillus	A genus of gram-negative, rod-shaped bacteria that derives energy from the oxidation of one or more reduced sulfur compounds. Many former species have been reclassified to other classes of PROTEOBACTERIA.	Thiobacillus denitrificans,Thiobacillus thioparus
D013912	Threonine	An essential amino acid occurring naturally in the L-form, which is the active form. It is found in eggs, milk, gelatin, and other proteins.	L-Threonine,L Threonine
D013913	Threonine Dehydratase	A pyridoxal-phosphate protein that catalyzes the deamination of THREONINE to 2-ketobutyrate and AMMONIA. The role of this enzyme can be biosynthetic or biodegradative. In the former role it supplies 2-ketobutyrate required for ISOLEUCINE biosynthesis, while in the latter it is only involved in the breakdown of threonine to supply energy. This enzyme was formerly listed as EC 4.2.1.16.	Threonine Deaminase,Threonine Dehydrase,Threonine Ammonia-Lyase,Ammonia-Lyase, Threonine,Deaminase, Threonine,Dehydrase, Threonine,Dehydratase, Threonine,Threonine Ammonia Lyase
D014633	Valine	A branched-chain essential amino acid that has stimulant activity. It promotes muscle growth and tissue repair. It is a precursor in the penicillin biosynthetic pathway.	L-Valine,L Valine