An atROL isomerase isomerises atROL to 11cROL

Stable Identifier
R-HSA-2465926
Type
Reaction [omitted]
Species
Homo sapiens
Compartment
cytosol, endoplasmic reticulum membrane
ReviewStatus
5/5
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An atROL isomerase isomerises atROL to 11cROL
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The canonical rod retinoid (visual) cycle is too slow to account for the photosensitivity of cones in bright light conditions. Novel enzyme activities demonstrated in ground-squirrel and chicken retinas produce a novel pathway of chromophore regeneration specific for cones. The first reaction in Muller cells, the isomerization of all-trans-retinol (atROL) to 11-cis-retinol (11cROL), is mediated by an as-yet-uncharacterised atROL isomerase (Mata et al. 2002, Mata et al. 2005). This reaction is proposed to take place in all vertebrates including humans (Wang & Kefalov 2009). Sphingolipid delta(4)-desaturase DES1 (DEGS1), an enzyme involved in sphingolipid de-novo biosynthesis, was recently found to possess retinoid isomerisation activity in chicken retinas but its physiological relevance in the synthesis of 11cROL remains inconclusive (Kaylor et al. 2013, Kiser et al. 2014).
Literature References
PubMed ID Title Journal Year
16128572 Chicken retinas contain a retinoid isomerase activity that catalyzes the direct conversion of all-trans-retinol to 11-cis-retinol

Travis, GH, Radu, RA, Mata, NL, Ruiz, A, Bui, TV

Biochemistry 2005
19781940 An alternative pathway mediates the mouse and human cone visual cycle

Kefalov, VJ, Wang, JS

Curr. Biol. 2009
23143414 Identification of DES1 as a vitamin A isomerase in Müller glial cells of the retina

Makshanoff, J, Habib, S, Travis, GH, Miu, A, Sarfare, S, Kim, A, Nusinowitz, S, Kim, P, Xu, T, Kaylor, JJ, Yuan, Q, Roybal, CN, Cook, J

Nat. Chem. Biol. 2013
12367507 Isomerization and oxidation of vitamin a in cone-dominant retinas: a novel pathway for visual-pigment regeneration in daylight.

Travis, GH, Radu, RA, Clemmons, RC, Mata, NL

Neuron 2002
23905688 Chemistry of the retinoid (visual) cycle

Kiser, PD, Golczak, M, Palczewski, K

Chem. Rev. 2014
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Output
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Catalyst Activity

retinol isomerase activity of atROL isomerase [endoplasmic reticulum membrane]

Physical Entity
atROL isomerase [endoplasmic reticulum membrane] (Homo sapiens)
Activity
retinol isomerase activity (GO:0050251)
Inferred From
Isomerase II isomerises atROL to 11cROL (Gallus gallus)
Authored
Jassal, B  (2012-09-04)
Reviewed
Blaner, WS  (2013-01-31)
Created
Jassal, B  (2012-09-04)
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