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Aliases ACAD9, NPD002, acyl-CoA dehydrogenase family member 9
External IDs MGI: 1914272 HomoloGene: 8539 GeneCards: ACAD9
Gene location (Human)
Chromosome 3 (human)
Chr. Chromosome 3 (human)[1]
Chromosome 3 (human)
Genomic location for ACAD9
Genomic location for ACAD9
Band 3q21.3 Start 128,879,596 bp[1]
End 128,916,067 bp[1]
Species Human Mouse
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC) Chr 3: 128.88 – 128.92 Mb Chr 3: 36.07 – 36.09 Mb
PubMed search [3] [4]
View/Edit Human View/Edit Mouse

Acyl-CoA dehydrogenase family member 9, mitochondrial is an enzyme that in humans is encoded by the ACAD9 gene.[5][6]


The ACAD9 gene contains an open reading frame of 1866 base pairs; this gene encodes a protein with 621 amino acid residues. Alignment of the ACAD9 protein sequence with that of other human ACAD proteins showed that ACAD-9 protein displays 46–27% identity, and 56–38% similarity with the eight members of the ACAD family, including ACADVL, ACADS, ACADM, ACADL, IVD, GCD, ACADSB, and ACD8. The calculated molecular weight of the ACAD9 is 68.8 kDa.[5]


The ACAD9 enzyme catalyzes a crucial step in fatty acid beta-oxidation by forming a C2-C3 trans-double bond in the fatty acid. LVCAD is specific to very long-chain fatty acids, typically C16-acylCoA and longer.[7] It has been observed that ACAD9 can catalyze acyl-CoAs with very long chains. The specific activity of ACAD9 towards palmitoyl-CoA (C16:0) is three times higher than that towards stearoyl-CoA (C18:0). ACAD-9 has little activity on n-octanoyl-CoA (C8:0), n-butyryl-CoA (C4:0) or isovaleryl-CoA (C5:0).[5]

In contrast with ACADVL, ACAD9 is also involved in assembly of the oxidative phosphorylation complex I. ACAD9 binds complex I assembly factors NDUFAF1 and Ecsit and is specifically required for the assembly of complex I. Furthermore, ACAD9 mutations result in complex I deficiency and not in disturbed long-chain fatty acid oxidation.[8]

Clinical significance[edit]

Mutations in the ACAD9 gene are associated with Mitochondrial Complex I Deficiency, which is autosomal recessive. This deficiency is the most common enzymatic defect of the oxidative phosphorylation disorders.[9][10] Mitochondrial complex I deficiency shows extreme genetic heterogeneity and can be caused by mutation in nuclear-encoded genes or in mitochondrial-encoded genes. There are no obvious genotype-phenotype correlations, and inference of the underlying basis from the clinical or biochemical presentation is difficult, if not impossible.[11] However, the majority of cases are caused by mutations in nuclear-encoded genes.[12][13] It causes a wide range of clinical disorders, ranging from lethal neonatal disease to adult-onset neurodegenerative disorders. Phenotypes include macrocephaly with progressive leukodystrophy, nonspecific encephalopathy, hypertrophic cardiomyopathy, myopathy, liver disease, Leigh syndrome, Leber hereditary optic neuropathy, and some forms of Parkinson disease.[14]

A few cases specific to ACAD9 have been reported. Some cases presented with episodic liver dysfunction during otherwise mild illnesses or cardiomyopathy, along with chronic neurologic dysfunction. Brain findings were notable for generalized edema with diffuse ventricular compression, acute left tonsillar herniation, and diffuse multifocal acute damage in the hippocampus. In addition, some abnormalities consistent with nonacute changes were seen, including a subacute right cerebellar hemispheric infarct and reduction in the number of neurons in several areas.[15] In one patient, whose clinical manifestations of hypotonia, cardiomyopathy, and lactic acidosis, a vigorous treatment with riboflavin allowed the individual to have normal psychomotor development and no cognitive impairment at 5 years of age.[16]


ACAD9 is part of the mitochondrial complex I assembly (MCIA) complex. The complex comprises at least TMEM126B, NDUFAF1, ECSIT, and ACAD9, which interacts directly with NDUFAF1 and ECSIT.[8]


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000177646 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000027710 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:". 
  4. ^ "Mouse PubMed Reference:". 
  5. ^ a b c Zhang J, Zhang W, Zou D, Chen G, Wan T, Zhang M, Cao X (Oct 2002). "Cloning and functional characterization of ACAD-9, a novel member of human acyl-CoA dehydrogenase family". Biochemical and Biophysical Research Communications. 297 (4): 1033–42. doi:10.1016/S0006-291X(02)02336-7. PMID 12359260. 
  6. ^ "Entrez Gene: ACAD9 acyl-Coenzyme A dehydrogenase family, member 9". 
  7. ^ Aoyama T, Souri M, Ushikubo S, Kamijo T, Yamaguchi S, Kelley RI, Rhead WJ, Uetake K, Tanaka K, Hashimoto T (Jun 1995). "Purification of human very-long-chain acyl-coenzyme A dehydrogenase and characterization of its deficiency in seven patients". The Journal of Clinical Investigation. 95 (6): 2465–73. doi:10.1172/JCI117947. PMC 295925Freely accessible. PMID 7769092. 
  8. ^ a b Nouws J, Nijtmans L, Houten SM, van den Brand M, Huynen M, Venselaar H, Hoefs S, Gloerich J, Kronick J, Hutchin T, Willems P, Rodenburg R, Wanders R, van den Heuvel L, Smeitink J, Vogel RO (Sep 2010). "Acyl-CoA dehydrogenase 9 is required for the biogenesis of oxidative phosphorylation complex I". Cell Metabolism. 12 (3): 283–94. doi:10.1016/j.cmet.2010.08.002. PMID 20816094. 
  9. ^ Kirby DM, Salemi R, Sugiana C, Ohtake A, Parry L, Bell KM, Kirk EP, Boneh A, Taylor RW, Dahl HH, Ryan MT, Thorburn DR (Sep 2004). "NDUFS6 mutations are a novel cause of lethal neonatal mitochondrial complex I deficiency". The Journal of Clinical Investigation. 114 (6): 837–45. doi:10.1172/JCI20683. PMC 516258Freely accessible. PMID 15372108. 
  10. ^ McFarland R, Kirby DM, Fowler KJ, Ohtake A, Ryan MT, Amor DJ, Fletcher JM, Dixon JW, Collins FA, Turnbull DM, Taylor RW, Thorburn DR (Jan 2004). "De novo mutations in the mitochondrial ND3 gene as a cause of infantile mitochondrial encephalopathy and complex I deficiency". Annals of Neurology. 55 (1): 58–64. doi:10.1002/ana.10787. PMID 14705112. 
  11. ^ Haack TB, Haberberger B, Frisch EM, Wieland T, Iuso A, Gorza M, Strecker V, Graf E, Mayr JA, Herberg U, Hennermann JB, Klopstock T, Kuhn KA, Ahting U, Sperl W, Wilichowski E, Hoffmann GF, Tesarova M, Hansikova H, Zeman J, Plecko B, Zeviani M, Wittig I, Strom TM, Schuelke M, Freisinger P, Meitinger T, Prokisch H (Apr 2012). "Molecular diagnosis in mitochondrial complex I deficiency using exome sequencing". Journal of Medical Genetics. 49 (4): 277–83. doi:10.1136/jmedgenet-2012-100846. PMID 22499348. 
  12. ^ Loeffen JL, Smeitink JA, Trijbels JM, Janssen AJ, Triepels RH, Sengers RC, van den Heuvel LP (2000). "Isolated complex I deficiency in children: clinical, biochemical and genetic aspects". Human Mutation. 15 (2): 123–34. doi:10.1002/(SICI)1098-1004(200002)15:2<123::AID-HUMU1>3.0.CO;2-P. PMID 10649489. 
  13. ^ Triepels RH, Van Den Heuvel LP, Trijbels JM, Smeitink JA (2001). "Respiratory chain complex I deficiency". American Journal of Medical Genetics. 106 (1): 37–45. doi:10.1002/ajmg.1397. PMID 11579423. 
  14. ^ Robinson BH (May 1998). "Human complex I deficiency: clinical spectrum and involvement of oxygen free radicals in the pathogenicity of the defect". Biochimica et Biophysica Acta. 1364 (2): 271–86. doi:10.1016/s0005-2728(98)00033-4. PMID 9593934. 
  15. ^ He M, Rutledge SL, Kelly DR, Palmer CA, Murdoch G, Majumder N, Nicholls RD, Pei Z, Watkins PA, Vockley J (Jul 2007). "A new genetic disorder in mitochondrial fatty acid beta-oxidation: ACAD9 deficiency". American Journal of Human Genetics. 81 (1): 87–103. doi:10.1086/519219. PMC 1950923Freely accessible. PMID 17564966. 
  16. ^ Haack TB, Danhauser K, Haberberger B, Hoser J, Strecker V, Boehm D, Uziel G, Lamantea E, Invernizzi F, Poulton J, Rolinski B, Iuso A, Biskup S, Schmidt T, Mewes HW, Wittig I, Meitinger T, Zeviani M, Prokisch H (Dec 2010). "Exome sequencing identifies ACAD9 mutations as a cause of complex I deficiency". Nature Genetics. 42 (12): 1131–4. doi:10.1038/ng.706. PMID 21057504. 

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