Sandbox Reserved 1549
From Proteopedia
| This Sandbox is Reserved from May 28 through July 01, 2019 for use in the course Advanced Biochemistry BCHM 4100 taught by Tom Gluick at the Georgia Gwinnett College. This reservation includes Sandbox Reserved 1544 through Sandbox Reserved 1555. |
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A Very Long Chain Acyl-CoA Dehydrogenase
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Function
Very long-chain acyl-CoA dehydrogenase (VLCAD) is one of the five members of acyl-CoA dehydrogenases (ACADs). VLCADs assembles the initial, rate limiting step of mitochondrial fatty acid β-oxidation[3]. The VLCAD has ideal chain length specificity in which fatty acyl-CoA has 16 carbons in length[3]. They are long-, medium-, and short-chain acyl CoA dehydrogenase[3]. In addition, the activation of acyl CoA dehydrogenase 9 (ACAD-9) is mostly with unsaturated long-chain acyl-CoAs[3]. Unlike other ACADs, mature VLCAD and ACAD-9 are homodimers of 67-kDa subunit which binds to the inner mitochondrial membrane[3]. VLCAD and ACAD- 9 possess an additional 180 residues on the C-terminal end, and also with other AVCADs, they possess MCAD-like catalytic glutamate[3]. In fact, not only allows longer chain-length substrates to bind, VLCAD prefers them to bind[3]. C-terminal domain of VLCAD has shown to be subjected for binding to the matrix side of the inner mitochondrial membrane[3]. A450P and L462P are human clinical mutants in which located in the C-terminal domain. When these mutants are active and stable, it is reducing the capability to bind the membrane[3]. However, there is no clear hydrophobic patch visible that can interact with the membrane, and are the residue that disordered the VLCAD structure[3]. Due to the proximity of , and it expects that the disordered residues occur at the surface of the molecule[3]. In addition, there are Gln-95 and Glu-99, in which located in MCAD, they help to form the base of the building cavity[3]. In VLCAD, these residues are called glycine (), in which efficiently open up and deepen the binding pocket[3].
Disease
VLCDA clinical mutation can lead to a disease state. VLCAD is used to break down very long-chain fatty acids, and they are found in food and body’s fat tissue [4]. Fatty acids play a crucial role which provides energy for heart and muscle [3]. Thus, VLCAD deficiency can cause severe neonatal cardiomyopathy and liver failure which occur mostly in adolescence or adulthood [3]. In addition, if the body does not have sufficient amount of VLCAD, it would affect the metabolism of the body [4]. There are several mutation sites that have been found. Mutation R429W is severe in childhood phenotype [3]. on the helix K makes salt-bridge with on helix I [3]. The enzyme is destabilized, and the salt bridge is broken due to the replacing charged residue with the bulky neutral residue [3]. Another mutation site is R416H which is found on the helix J [3]. Both sites,, are located close to the [3]. Site R416H has by making salt bridge and interacts through hydrogen bond [3]. Mutation in R416H causes the problem to the position of helix J [3]. Furthermore, forming a salt bridge with the opposing monomer can affect the dimer interaction [3].
Deficient VLCAD affects 1 person in 40,000 to 120,000 people, thus, it is a very rare diseases [4].
Structural highlights
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VLCAD is a mitochondrial inner-membrane-associated protein and is a homodimer of a 71-kDa polypeptide containing 2 mol FAD/mol enzyme [5]
