“…However, finding a sequence with specific desired properties can be difficult, particularly when only a few members of a protein family have been characterized and a detailed understanding of the structure-function relationship is lacking. The ketol-acid reductoisomerase (KARI, EC 1.1.1.86, also known as acetohydroxyacid isomeroreductase (AHAIR)) enzymes have attracted much interest for production of amino acids and biofuels (Atsumi et al, 2008a;Bastian et al, 2011;Brinkmann-Chen et al, 2013;Hasegawa et al, 2012;Liu et al, 2010). These oxidoreductases catalyze the second step in the branched chain amino-acid (BCAA) biosynthesis pathway (Chunduru et al, 1989), conversion of (S)-2-acetolactate (S2AL) to (R)-2,3-dihydroxyisovalerate (RDHIV) via a methyl shift coupled to a reduction with concomitant oxidation of a nicotinamide adenine dinucleotide cofactor.…”