|
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 |
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