Ketoisovalerate reductase; part of the gene cluster that mediates the biosynthesis of beauvericin (BEA), a non-ribosomal cyclic hexadepsipeptide that shows antibiotic, antifungal, insecticidal, and cancer cell antiproliferative and antihaptotactic activity (PubMed:18804027, PubMed:19105175, PubMed:27449895). Ketoisovalerate reductase BEA2 catalyzes the NADPH-specific reduction of ketoisovaleric acid to hydroxyisovalerate, a precursor for beauvericin biosynthesis (PubMed:19105175, PubMed:27449895). The nonribosomal cyclodepsipeptide synthetase BEA1 then catalyzes the formation of beauvericin via condensation and cyclization of 3 dipeptidol monomers, each composed of one unit of hydroxyisovalerate and one unit of N-methyl-phenylalanine (PubMed:18804027, PubMed:28534477). (R)-2-hydroxy-3-methylbutyrate + NADP(+) = 3-methyl-2-oxobutanoate + H(+) + NADPH Environmental stimuli such as light and salt stress suppress activity through stimulation of calmodulin (CaM) that binds BEA2 and probably impairs its dimerization. Optimum pH is 7.5. Optimum temperature is 35 degrees Celsius. Homodimer (Probable). Binds to calmodulin in a calcium-independent manner (PubMed:27449895). Impairs the production of both beauvericin and bassianolide. Belongs to the ketopantoate reductase family.