<p> This model represents largely uncharacterised proteins related to 2-isopropylmalate synthases and homocitrate synthases but that are phylogenetically distinct. Homocitrate synthase belongs in the alpha-aminoadipate pathway of lysine synthesis. 2-isopropylmalate synthase, with potassium as a cofactor, catalyses the reaction: <reaction>acetyl-CoA + 3-methyl-2-oxobutanoate + H2O = (2S)-2-isopropylmalate + CoA</reaction> </p>