3-hydroxy-3-methylglutaryl-CoA lyase

Hydroxymethylglutaryl-CoA lyase

HMG-CoA lyase dimer, Human
EC number
CAS number 9030-83-5
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO
3-hydroxymethyl-3-methylglutaryl-Coenzyme A lyase (hydroxymethylglutaricaciduria)
Symbol HMGCL
Entrez 3155
HUGO 5005
OMIM 246450
RefSeq NM_000191
UniProt P35914
Other data
EC number
Locus Chr. 1 p36.1-p35

3-hydroxy-3-methylglutaryl-CoA lyase (or HMG-CoA lyase) is an enzyme that in human is encoded by the HMGCL gene located on chromosome 1. It is a key enzyme in ketogenesis (ketone body formation).


The HMGCL gene encodes a 34.5-kDa protein that is localized to the mitochondrion and peroxisome.[1] Multible isoforms of the proteins are known due to alternative splicing. The major isoform (isoform 1) is most highly expressed in the liver [2] whereas isoform 2 is found in energy-demanding tissues including the brain, heart, and skeletal muscle.[3]

Structure of the HMGCL protein has been resolved by X-ray crystallography at 2.1-Å resolution, and reveals that the protein may function as a dimer. Substrate access to the active site of the HMGCL enzyme involves substrate binding across a cavity located at the C-terminal end of a beta barrel structure.[4] In addition, the lysine 48 residue which is mutated in patients with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency is also found to be necessary for substrate binding.[5]


The HMGCL protein plays an essential role in breaking down dietary proteins and fats for energy. It catalyzes the reaction:

(S)-3-hydroxy-3-methylglutaryl-CoA = acetyl-CoA + acetoacetate.

and requires a divalent metal ion as co-factor.[6]

The enzyme is required for ketogenesis in the liver, and is also responsible for processing the amino acid leucine inside the mitochondrion

Clinical Significance

Mutations in the HMGCL gene cause 3-hydroxy-3-methylglutaryl-CoA lyase deficiency (HMGCLD), a rare autosomal recessive inborn error of metabolism characterized by disruption of ketogenesis and L-leucine catabolism. To-date more than 30 different mutations including missense mutations of different residues have been associated with patients with HMGCLD in diverse families and ethnicities.[7] HMGCLD typically presents in the first year of the patient's life after a fasting period. Clinical acute symptoms include vomiting, seizures, metabolic acidosis, hypoketotic hypoglycemia, and lethargy.[8]


HMGCL interacts with itself to form homodimers and homotetramers. It is also shown in yeast two-hybrid experiments to interact with DNAJA1.


  1. Ashmarina LI, Robert MF, Elsliger MA, Mitchell GA (1996). "Characterization of the hydroxymethylglutaryl-CoA lyase precursor, a protein targeted to peroxisomes and mitochondria". Biochem. J. 315 ( Pt 1): 71–5. PMC 1217198Freely accessible. PMID 8670134.
  2. Ashmarina LI, Robert MF, Elsliger MA, Mitchell GA (1996). "Characterization of the hydroxymethylglutaryl-CoA lyase precursor, a protein targeted to peroxisomes and mitochondria". Biochem. J. 315 ( Pt 1): 71–5. PMC 1217198Freely accessible. PMID 8670134.
  3. Puisac B, Ramos M, Arnedo M, Menao S, Gil-Rodríguez MC, Teresa-Rodrigo ME, Pié A, de Karam JC, Wesselink JJ, Giménez I, Ramos FJ, Casals N, Gómez-Puertas P, Hegardt FG, Pié J (2012). "Characterization of splice variants of the genes encoding human mitochondrial HMG-CoA lyase and HMG-CoA synthase, the main enzymes of the ketogenesis pathway". Mol. Biol. Rep. 39 (4): 4777–85. doi:10.1007/s11033-011-1270-8. PMID 21952825.
  4. Fu Z, Runquist JA, Montgomery C, Miziorko HM, Kim JJ (2010). "Functional insights into human HMG-CoA lyase from structures of Acyl-CoA-containing ternary complexes". J. Biol. Chem. 285 (34): 26341–9. doi:10.1074/jbc.M110.139931. PMC 2924059Freely accessible. PMID 20558737.
  5. Carrasco P, Menao S, López-Viñas E, Santpere G, Clotet J, Sierra AY, Gratacós E, Puisac B, Gómez-Puertas P, Hegardt FG, Pie J, Casals N (2007). "C-terminal end and aminoacid Lys48 in HMG-CoA lyase are involved in substrate binding and enzyme activity". Mol. Genet. Metab. 91 (2): 120–7. doi:10.1016/j.ymgme.2007.03.007. PMID 17459752.
  6. Tuinstra RL, Miziorko HM (2003). "Investigation of conserved acidic residues in 3-hydroxy-3-methylglutaryl-CoA lyase: implications for human disease and for functional roles in a family of related proteins". J. Biol. Chem. 278 (39): 37092–8. doi:10.1074/jbc.M304472200. PMID 12874287.
  7. Menao S, López-Viñas E, Mir C, Puisac B, Gratacós E, Arnedo M, Carrasco P, Moreno S, Ramos M, Gil MC, Pié A, Ribes A, Pérez-Cerda C, Ugarte M, Clayton PT, Korman SH, Serra D, Asins G, Ramos FJ, Gómez-Puertas P, Hegardt FG, Casals N, Pié J (2009). "Ten novel HMGCL mutations in 24 patients of different origin with 3-hydroxy-3-methyl-glutaric aciduria". Human Mutation. 30 (3): E520–9. doi:10.1002/humu.20966. PMID 19177531.
  8. http://www.omim.org/entry/246450[]

External links

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