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J. Bacteriol., Jan 1996, 19-23, Vol 178, No. 1
KM Bischoff and VW Rodwell
Prior work from this laboratory characterized eukaryotic (hamster) and
eubacterial (Pseudomonas mevalonii) 3-hydroxy-3-methylglutaryl-coenzyme A
(HMG-CoA) reductases. We report here the characterization of an HMG- CoA
reductase from the third domain, the archaea. HMG-CoA reductase of the
halobacterium Haloferax volcanii was initially partially purified from
extracts of H. volcanii. Subsequently, a portion of the H. volcanii
lovastatin (formerly called mevinolin) resistance marker mev was subcloned
into the Escherichia coli expression vector pT7-7. While no HMG-CoA
reductase activity was detectable following expression in E. coli, activity
could be recovered after extracts were exposed to 3 M KCl. Following
purification to electrophoretic homogeneity, the specific activity of the
expressed enzyme, 24 microU/mg, equaled that of homogeneous hamster or P.
mevalonii HMG-CoA reductase. Activity was optimal at pH 7.3. Kms were 66
microM (NADPH) and 60 microM [(S)-HMG- CoA]. (R)-HMG-CoA and lovastatin
inhibited competitively with (S)-HMG- CoA. H. volcanii HMG-CoA reductase
also catalyzed the reduction of mevaldehyde [optimal activity at pH 6.0;
Vmax 11 microU/mg; Kms 32 microM (NADPH), 550 microM [(R,S)-mevaldehyde]]
and the oxidative acylation of mevaldehyde [optimal activity at pH 8.0;
Vmax 2.1 microU/mg; Kms 350 microM (NADP+), 300 microM (CoA), 470 microM
[(R,S)- mevaldehyde]]. These properties are comparable to those of hamster
and P. mevalonii HMG-CoA reductases, suggesting a similar catalytic
mechanism.
Copyright © 1996, American Society for Microbiology
3-Hydroxy-3-methylglutaryl-coenzyme A reductase from Haloferax volcanii: purification, characterization, and expression in Escherichia coli
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153, USA.
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