= 11-cis-retinol
<11-cis-retinol> is a geometric isomer of <retinol> with the cis configuration at the double bond identified by position 11 in conventional retinoid numbering. It retains the alcohol group and the formula $\mathrm{C_{20}H_{30}O}$. The contrast with <all-trans-retinol> concerns spatial arrangement rather than a change in elemental composition.<11-cis-retinol in ChEBI>[CHEBI:16302, structure and formula]{ref}<All-trans-retinol in ChEBI>[CHEBI:17336, trans geometry and formula]{ref}
It is a measured product of <RPE65> activity in the <visual cycle>. In a 2005 study, recombinant expression in cultured cells generated this product when the system also supplied the required <all-trans-retinyl ester> substrate.<RPE65 is the isomerohydrolase in the retinoid visual cycle by Gennadiy Moiseyev and others>[Abstract, recombinant conversion and substrate requirement]{ref}
The alcohol must also be distinguished from the aldehyde <11-cis-retinal>. Their similar names identify related compounds, not the same oxidation state. Likewise, a mass measurement alone cannot distinguish every retinol geometric isomer: <11-cis-retinol> and <all-trans-retinol> have the same formula. An interpretation of the enzyme experiment needs product identification that resolves the chemical distinction being claimed, rather than simply detecting some vitamin-A-related material.
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