|
type |
Journal Article |
authors |
Whalen, W. A.; Berg, C. M. |
title |
Analysis of an avtA::Mu d1(Ap lac) mutant: metabolic role of transaminase C |
journal |
J Bacteriol |
Activity |
2.6.1.66 |
ui |
82167178 |
year |
(1982) |
volume |
150 |
number |
2 |
pages |
739-46. |
| |
keywords |
Aminobutyric Acids/metabolism |
abstract |
Escherichia coli can synthesize alpha-ketoisovalerate, the precursor of valine, leucine, and pantothenate, by three routes: anabolically via dihydroxyacid dehydrase and catabolically via both the branched-chain amino acid transaminase (transaminase B) and the alanine-valine transaminase (transaminase C). An E. coli K-12 mutant devoid of transaminase C (avtA) was isolated by mutagenizing an isoleucine- requiring strain devoid of transaminase B (ilvE::Tn5) with Mu d1(Ap lac) and selecting for valine-requiring derivatives which were ampicillin resistant, Lac+, able to crossfeed an ilvD mutant, and unable to grow on alpha-ketoisovalerate in place of valine. Strains defective in one, two, or all three alpha-ketoisovalerate metabolic enzymes were constructed, and their properties were analyzed. The data indicated that avtA is the structural gene for transaminase C, that transaminase C is a single enzyme species, and that the sole pathway for pantothenate biosynthesis is from alpha-ketoisovalerate. The data further showed that isoelectric inhibits the transaminase B-catalyzed deamination of valine in vivo. |
last changed |
2002/11/02 00:35 |
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