The function of FMO5 (flavin containing dimethylaniline monoxygenase 5, Ensembl gene identifier ENSG00000131781) is as follows. Acts as a Baeyer-Villiger monooxygenase on a broad range of substrates. Catalyzes the insertion of an oxygen atom into a carbon- carbon bond adjacent to a carbonyl, which converts ketones to esters (PubMed:20947616, PubMed:26771671, PubMed:28783300). Active on diverse carbonyl compounds, whereas soft nucleophiles are mostly non- or poorly reactive (PubMed:26771671, PubMed:7872795). In contrast with other forms of FMO it is non- or poorly active on 'classical' substrates such as drugs, pesticides, and dietary components containing soft nucleophilic heteroatoms (Probable) (PubMed:7872795). Able to oxidize drug molecules bearing a carbonyl group on an aliphatic chain, such as nabumetone and pentoxifylline (PubMed:28783300). Also, in the absence of substrates, shows slow but yet significant NADPH oxidase activity (PubMed:26771671). Acts as a positive modulator of cholesterol biosynthesis as well as glucose homeostasis, promoting metabolic aging via pleiotropic effects (By similarity). {ECO:0000250|UniProtKB:P97872, ECO:0000269|PubMed:20947616, ECO:0000269|PubMed:26771671, ECO:0000269|PubMed:28783300, ECO:0000269|PubMed:7872795, ECO:0000305|PubMed:26771671}.