>TIGR02090 LEU1_arch isopropylmalate/citramalate/homocitrate synthases; InterPro: IPR011830 Methanogenic archaea contain three closely related homologs of the 2-isopropylmalate synthases (LeuA) represented by IPR005671 from INTERPRO. Two of these in Methanococcus janaschii (MJ1392 - CimA ; MJ0503 - AksA ) have been characterised as catalyzing alternative reactions leaving the third (MJ1195) as the presumptive LeuA enzyme. CimA is citramalate (2-methylmalate) synthase, which condenses acetyl-CoA with pyruvate. This enzyme is believed to be involved in the biosynthesis of isoleucine in methanogens and possibly other species lacking threonine dehydratase. AksA is a homocitrate synthase which also produces (homo)2-citrate and (homo)3-citrate in the biosynthesis of Coenzyme B which is restricted solely to methanogenic archaea. Methanogens, then should and apparently do contain all three of these enzymes. Unfortunately, phylogenetic trees do not resolve into three unambiguous clades, making assignment of function to particular genes problematic. Other archaea, which lack a threonine dehydratase (mainly Euryarchaeota), should contain both CimA and LeuA genes. This is true for archaeoglobus fulgidis, but not for the Pyrococci which have none in this clade, but one in IPR005671 from INTERPRO and one in IPR005675 from INTERPRO which may fulfil these roles. Proteins from other species, which have only one hit to this entry and lack threonine dehydratase, are very likely to be LeuA enzymes.; GO: 0046912 transferase activity transferring acyl groups acyl groups converted into alkyl on transfer, 0019752 carboxylic acid metabolic process.

Probab=95.66  E-value=0.022  Score=37.59  Aligned_cols=52  Identities=21%  Similarity=0.315  Sum_probs=38.6

Q ss_pred             HHHHHHHHHCCCCEEEECCCCHHHCCHHHHHHHHCCCHHHHHHHHHHHCCCCEEECCCCC
Q ss_conf             999777775498167843831100683567776127226899998630886236024311
Q gi|254780812|r  189 AEYLIAQIHAGVDVIQIFDTHAGCLGEHEFENYAARSVGRIISAVRRKYPNAKFISFAKG  248 (346)
Q Consensus       189 ~~yl~~Qi~aGad~iqIFDs~ag~Ls~~~f~~f~~p~~kkI~~~ik~~~~~vpiI~f~~g  248 (346)
T Consensus       146 Ik~~k~A~eAGADRi~~~DT-VGV~~P~km~~l~----k~~k~~~kK---d~~~sVHCHN  197 (371)
T TIGR02090       146 IKVFKKAEEAGADRINVADT-VGVLTPQKMEELI----KKIKENVKK---DLPVSVHCHN  197 (371)
T ss_pred             HHHHHHHHHCCCCEEEECCC-CCCCCHHHHHHHH----HHHHHHHCC---CCCEEEEEEC
T ss_conf             99987133216777550785-5636826799999----999986358---8705886208