Retinoid isomerohydrolase

RPE65 (gene name)
Plays important roles in the production of 11-cis retinal and in visual pigment regeneration.
The soluble form binds vitamin A (all-trans-retinol), making it available for LRAT (Lecithin retinol acyltransferase) processing to all-trans-retinyl ester. The membrane form, palmitoylated by LRAT, binds all-trans-retinyl esters, making them available for IMH (isomerohydrolase) processing to all-cis-retinol. The soluble form is regenerated by transferring its palmitoyl groups onto 11-cis-retinol, a reaction catalyzed by LRAT. The enzymatic activity is linearly dependent of the expression levels and membrane association.

Catalytic activity

An all-trans-retinyl ester + H2O = 11-cis-retinol + a fatty acid.

Subcellular location

  • Cytoplasm
  • Cell membrane; Lipid-anchor
  • Microsome membrane

Note: Attached to the membrane by a lipid anchor when palmitoylated (membrane form), soluble when unpalmitoylated (By similarity). Undergoes light-dependent intracellular transport to become more concentrated in the central region of the retina pigment epithelium cells.

Leber congenital amaurosis 2 (LCA2)

The disease is caused by mutations affecting the gene represented in this entry.
A severe dystrophy of the retina, typically becoming evident in the first years of life. Visual function is usually poor and often accompanied by nystagmus, sluggish or near-absent pupillary responses, photophobia, high hyperopia and keratoconus.
See also OMIM:204100

Retinitis pigmentosa 20 (RP20)

The disease is caused by mutations affecting the gene represented in this entry.
A retinal dystrophy belonging to the group of pigmentary retinopathies. Retinitis pigmentosa is characterized by retinal pigment deposits visible on fundus examination and primary loss of rod photoreceptor cells followed by secondary loss of cone photoreceptors. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well.
See also OMIM:613794