Cloning of genomic and cDNA for mouse isovaleryl-CoA dehydrogenase (IVD) and evolutionary comparison to other known IVDs.

Isovaleryl-CoA dehydrogenase (IVD) is an intramitochondrial homotetrameric flavoenzyme that catalyzes the conversion of isovaleryl-CoA to 3-methylcrotonyl-CoA in the leucine catabolism pathway. Deficiency of IVD in humans causes isovaleric acidemia, which shows tremendous clinical variability for reasons that are unknown. To help better understand this disorder, we have cloned and sequenced the mouse IVD genomic and cDNAs. The mouse IVD gene spans approximately 17 kb and contains 12 coding exons organized identically to the human gene. It maps to mouse chromosome 2 in the area of band 2E4-E5, corresponding to the syntenic region of human chromosome 15. Mouse IVD predicted amino acid sequences are 95.8 and 89.6% identical to that of the rat and human sequences, respectively, with conservation of key functional residues. We have now identified IVD sequences from seven species. Comparison of these sequences shows that the rat and mouse proteins are the most closely related, both of which, in turn, share highest homology to human. All of the mammalian enzymes appear to be more closely related than any of the IVDs on other branches of the phylogram, while the fly and worm IVDs are the most divergent. The invertebrate IVDs are more closely related to the mammalian enzymes than to those from two plant species.