Vitamin A2 Explained

Vitamin A₂ is a subcategory of vitamin A.^[1]

As with all vitamin A forms, A₂ can exist as an aldehyde, Dehydroretinal (3,4-dehydroretinal), an alcohol, 3,4-dehydroretinol (vitamin A₂ alcohol) or an acid, 3,4-dehydroretinoic acid (vitamin A₂ acid). Many cold-blooded vertebrates use the aldehyde for their visual system to obtain a red-shifted sensitive spectrum.

Human skin naturally contains the alcohol form.^{[2] [3]} In humans, CYP27C1 converts ordinary A₁ (all-trans retinoids) to A₂. The enzyme also converts 11-cis-retinal.^[4]

Vitamin A₂ was first identified by Richard Alan Morton using newly-developed absorption spectroscopy in 1941.^[5]

Notes and References

1. Babino D, Golczak M, Kiser PD, Wyss A, Placzewski K, von Lintig J . The Biochemical Basis of Vitamin A3 Production in Arthropod Vision . ACS Chem Biol . 11 . 4 . 1049–1057 . 2016. 26811964 . 10.1021/acschembio.5b00967. 4841470 .
2. Törmä H, Vahlquist A . Biosynthesis of 3-dehydroretinol (vitamin A2) from all-trans-retinol (vitamin A1) in human epidermis . J Invest Dermatol . 85 . 6 . 498–500 . 1985. 4067325 . 10.1111/1523-1747.ep12277290. free .
3. Vahlquist A . The identification of dehydroretinol (vitamin A2) in human skin . Experientia . 36 . 3 . 317–318 . 1980 . 7371787 . 10.1007/bf01952299. 31357743 .
4. Kramlinger . VM . Nagy . LD . Fujiwara . R . Johnson . KM . Phan . TT . Xiao . Y . Enright . JM . Toomey . MB . Corbo . JC . Guengerich . FP . Human cytochrome P450 27C1 catalyzes 3,4-desaturation of retinoids. . FEBS Letters . May 2016 . 590 . 9 . 1304–12 . 10.1002/1873-3468.12167 . 27059013. 4864060 . free .
5. Goodwin . T W . R. A. Morton . Nature . 1977 . 266 . 5600 . 394 . 10.1038/266394a0 . 1977Natur.266..394G . 31211784 . free .