type	Journal Article
authors	Proteau, G.; Silver, M.
title	Effects of amino acids on Thiobacillus acidophilus. II. Threonine deaminase
journal	Can J Microbiol
Activity	4.3.1.19
Family	4.3.1.19
ui	81001496
year	(1980)
volume	26
number	3
pages	385-8.
keywords	Binding Sites
abstract	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.
last changed	2008/04/01 16:02