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:27750383). Ketoisovalerate reductase BEA2 catalyzes the NADPH-specific reduction of ketoisovaleric acid to hydroxyisovalerate, a precursor for beauvericin biosynthesis (By similarity). 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 (By similarity). (R)-2-hydroxy-3-methylbutyrate + NADP(+) = 3-methyl-2-oxobutanoate + H(+) + NADPH Expression is highly repressed by the histone deacetylase HDA1 and the beauvericin cluster-specific repressor BEA4 (PubMed:27750383). BEA biosynthesis is also repressed by the activity of the H3K27 methyltransferase KMT6 (PubMed:27750383). Decreases the production of beauvericin (PubMed:27750383). Belongs to the ketopantoate reductase family.