An atROL isomerase isomerises atROL to 11cROL

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R-HSA-2465926
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Reaction [omitted]
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Homo sapiens
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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
19781940 An alternative pathway mediates the mouse and human cone visual cycle

Wang, JS, Kefalov, VJ

Curr. Biol. 2009
16128572 Chicken retinas contain a retinoid isomerase activity that catalyzes the direct conversion of all-trans-retinol to 11-cis-retinol

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

Biochemistry 2005
23143414 Identification of DES1 as a vitamin A isomerase in Müller glial cells of the retina

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

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

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

Neuron 2002
23905688 Chemistry of the retinoid (visual) cycle

Kiser, PD, Golczak, M, Palczewski, K

Chem. Rev. 2014
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Title
retinol isomerase activity of atROL isomerase [endoplasmic reticulum membrane]
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