Involved in the biosynthesis of the azoxy antibiotic valanimycin, which has an antitumor activity (PubMed:9056232, PubMed:8990292, PubMed:9287340). Catalyzes the oxidation of isobutylamine to isobutylhydroxylamine via the formation of a flavin 4a-hydroperoxide (PubMed:9056232, PubMed:8990292, PubMed:9287340). Unlike other known N-hydroxylases, isobutylamine N-hydroxylase cannot carry out the reduction of the flavin cofactor and requires the NADPH-flavin oxidoreductase VlmR (PubMed:9056232). Also able to oxidize propan-1-amine, butan-1-amine, butan-2-amine and benzylamine (PubMed:9056232). It has a similar activity with either FMNH(2) or FADH(2) (PubMed:9056232). 2-methylpropan-1-amine + FADH2 + O2 = FAD + 2 H(+) + H2O + N-(2-methylpropyl)hydroxylamine 2-methylpropan-1-amine + FMNH2 + O2 = FMN + 2 H(+) + H2O + N-(2-methylpropyl)hydroxylamine Inhibited by 5',5'-dithio-bis(2-nitrobenzoic acid) (DTNB) and 4-(hydroxymercuri)benzoic acid (p-HMB). Exists in dimeric or trimeric form depending upon buffer conditions (PubMed:9056232). It can form an isobutylamine N-hydroxylase two component enzyme system formed of a flavin reductase component (VlmR) and a monooxygenase component (VlmH).