Efficiently catalyzes the conversion of all-trans retinol (also called vitamin A1, the precursor of 11-cis retinal) to 3,4-didehydroretinol (also called vitamin A2, the precursor of 11-cis 3,4-didehydroretinal), also acts on all-trans retinal and all-trans retinoic acid. The replacement of 11-cis retinal chromophore in photopigments with 11-cis 3,4-didehydroretinal enhances sensitivity to long-wavelength light. This may improve vision in fresh water which is often turbid. all-trans-retinol + 2 H(+) + O2 + 2 reduced [adrenodoxin] = all-trans-3,4-didehydroretinol + 2 H2O + 2 oxidized [adrenodoxin] Expressed in the dorsal third of retinal pigment epithelium, but not in the ventral counterpart (at protein level). Belongs to the cytochrome P450 family. Seeing through the murk - Issue 192 of June 2017