Publications

• Enzymology and evolution of the pyruvate pathway to 2-oxobutyrate in Methanocaldococcus jannaschii.

  Drevland R.M., Waheed A., Graham D.E.

  The archaeon Methanocaldococcus jannaschii uses three different 2-oxoacid elongation pathways, which extend the chain length of precursors in leucine, isoleucine, and coenzyme B biosyntheses. In each of these pathways an aconitase-type hydrolyase catalyzes an hydroxyacid isomerization reaction. Th ... >> More

  The archaeon Methanocaldococcus jannaschii uses three different 2-oxoacid elongation pathways, which extend the chain length of precursors in leucine, isoleucine, and coenzyme B biosyntheses. In each of these pathways an aconitase-type hydrolyase catalyzes an hydroxyacid isomerization reaction. The genome sequence of M. jannaschii encodes two homologs of each large and small subunit that forms the hydrolyase, but the genes are not cotranscribed. The genes are more similar to each other than to previously characterized isopropylmalate isomerase or homoaconitase enzyme genes. To identify the functions of these homologs, the four combinations of subunits were heterologously expressed in Escherichia coli, purified, and reconstituted to generate the iron-sulfur center of the holoenzyme. Only the combination of MJ0499 and MJ1277 proteins catalyzed isopropylmalate and citramalate isomerization reactions. This pair also catalyzed hydration half-reactions using citraconate and maleate. Another broad-specificity enzyme, isopropylmalate dehydrogenase (MJ0720), catalyzed the oxidative decarboxylation of beta-isopropylmalate, beta-methylmalate, and d-malate. Combined with these results, phylogenetic analysis suggests that the pyruvate pathway to 2-oxobutyrate (an alternative to threonine dehydratase in isoleucine biosynthesis) evolved several times in bacteria and archaea. The enzymes in the isopropylmalate pathway of leucine biosynthesis facilitated the evolution of 2-oxobutyrate biosynthesis through the introduction of a citramalate synthase, either by gene recruitment or gene duplication and functional divergence. << Less

  J. Bacteriol. 189:4391-4400(2007) [PubMed] [EuropePMC]

  This publication is cited by 7 other entries.

• Screening for microorganisms producing D-malate from maleate.

  van der Werf M.J., van den Tweel W.J., Hartmans S.

  More than 300 microorganisms were screened for their ability to convert maleate into D-malate as a result of the action of maleate hydratase. Accumulation of fumarate during incubation of permeabilized cells with maleate was shown to be indicative of one of the two enzymes known to transform malea ... >> More

  More than 300 microorganisms were screened for their ability to convert maleate into D-malate as a result of the action of maleate hydratase. Accumulation of fumarate during incubation of permeabilized cells with maleate was shown to be indicative of one of the two enzymes known to transform maleate. The ratio in which fumarate and malate accumulated could be used to estimate the enantiomeric composition of the malate formed. Many strains (n = 128) were found to be capable of converting maleate to D-malate with an enantiomeric purity of more than 97%. Pseudomonas pseudoalcaligenes NCIMB 9867 was selected for more detailed studies. Although this strain was not able to grow on maleate, permeabilized cells were able to degrade maleate to undetectable levels, with a concomitant formation of D-malate. The D-malate was formed with an enantiomeric purity of more than 99.97%. << Less

  Appl Environ Microbiol 58:2854-2860(1992) [PubMed] [EuropePMC]