Retinal isomerase

Retinal Isomerase

Retinal isomerase, also known as retinol isomerase or retinoid isomerase, is an enzyme that plays a crucial role in the visual cycle. It is responsible for the isomerization of all-trans-retinal to 11-cis-retinal, a process that is essential for the regeneration of visual pigments in the retina.

Function

Retinal isomerase is primarily found in the retinal pigment epithelium (RPE) and the photoreceptor cells of the retina. Its main function is to convert the all-trans-retinal, which is produced during the process of phototransduction, back into 11-cis-retinal. This isomerization reaction is a vital step in the visual cycle, as it allows the regeneration of the visual pigments necessary for vision.

Mechanism

The mechanism of retinal isomerase involves a series of chemical reactions that occur within the active site of the enzyme. The all-trans-retinal molecule binds to the enzyme, and through a series of rearrangements, it is converted into 11-cis-retinal. This isomerization reaction involves the rotation of a double bond within the retinal molecule, resulting in the formation of the cis configuration.

Importance in Vision

The isomerization of retinal by retinal isomerase is crucial for the visual system to function properly. The 11-cis-retinal produced by this enzyme is a key component of visual pigments, such as rhodopsin, found in the photoreceptor cells of the retina. When light enters the eye and strikes these visual pigments, it triggers a cascade of events that ultimately leads to the generation of electrical signals, which are then transmitted to the brain for visual perception.

Clinical Significance

Mutations or deficiencies in retinal isomerase can lead to various visual disorders. One such disorder is known as fundus albipunctatus, which is characterized by delayed dark adaptation due to impaired regeneration of visual pigments. Another condition associated with retinal isomerase dysfunction is Oguchi disease, a rare form of congenital stationary night blindness.

References

1. Visual cycle - A comprehensive overview of the visual cycle and its components. 2. Retinal pigment epithelium - The retinal pigment epithelium and its role in retinal function. 3. Photoreceptor cell - The structure and function of photoreceptor cells in the retina.

See Also

• Rhodopsin - The visual pigment that contains 11-cis-retinal.
• Phototransduction - The process by which light is converted into electrical signals in the retina.
• Congenital stationary night blindness - A group of inherited retinal disorders affecting night vision.

Templates

This visual system related article is a stub. You can help WikiMD by expanding it.