A Possible Vitamin A2

Edisbury, J. R.; Morton, R. A.; Simpkins, G. W.

doi:10.1038/140234a0

Cited by 47 publications

(15 citation statements)

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“…On turnto them, I found another visual pigment, porphyropsin, engaged in a cycle parallel with that of rhodopsin, but in which new carotenoids replace retinal and vitamin A (21). On the basis of these observations, it was suggested that the substance that replaces vitamin A in the visual system of freshwater fishes be called vitamin A2 (22). In what follows I shall call it retinol2, and its aldehyde retinal2.…”

Section: Backgroundsmentioning

confidence: 96%

Molecular Basis of Visual Excitation

Wald

1968

Science

1,026

587

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Section: Backgroundsmentioning

confidence: 96%

Molecular Basis of Visual Excitation

Wald

1968

Science

1,026

587

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“…It has emerged that the porphyropsin system constitutes a cycle of precisely the same form as the rhodopsin system, in which, however, vitamin A 1 and retinen% are replaced by new carotenoids Shortly after the properties of these new substances were first announced (Wald, 1937b) it was suggested that the vitamin AI~ analogue be called vitamin A 2 (Edisbury, Morton ~ Simpkins, 1937). The retinene~analogue in the porphyropsin cycle may correspondingly be called retinen%.…”

Section: Porphyropsinmentioning

confidence: 99%

The photochemistry of vision

Wald

1949

Doc Ophthalmol

149

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“…Since the 696 m/z chromogen replaces vitamin A in the retinal cycle of fresh-water fishes, Edisbury, Morton, and Simpkins (1937) have suggested that it be called vitamin A~. ~ The retinene-analogue in these fishes may correspondingly be called fetishes.…”

Section: Vitamin a ~ And Raine~mentioning

confidence: 99%

The Porphyropsin Visual System

Wald

1939

Journal of General Physiology

113

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1. In the rods of fresh-water and some anadromous fishes, rhodopsin is replaced by the purple photolabile pigment porphyropsin. This participates in a retinal cycle identical in form with that of rhodopsin, but in which new carotenoids replace retinene and vitamin A. 2. Porphyropsin possesses a broad absorption maximum at 522 ± 2 mµ, and perhaps a minimum at about 430 mµ. The vitamin A-analogue, vitamin A2, possesses a maximum in chloroform at 355 mµ and yields with antimony trichloride a deep blue color due to a band at 696 mµ. The retinene-analogue, retinene2, absorbs maximally in chloroform at 405 mµ and possesses an antimony chloride maximum at 706 mµ. 3. Its non-diffusibility through a semi-permeable membrane, salting-out properties, and sensitivity to chemical denaturants and to heat, characterize porphyropsin as a conjugated carotenoid-protein. 4. The porphyropsin cycle may be formulated: porphyropsin See PDF for Structure. retinene2-protein (2)→ vitamin A2-protein (3)→ porphyropsin. Isolation of the retina cuts this cycle at (3); denaturation procedures or extraction of porphyropsin into aqueous solution eliminate in addition (1) and (2). 5. The primary difference between the rhodopsin and porphyropsin systems appears to be the possession by the latter of an added ethylenic group in the polyene chain.

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A Possible Vitamin A2

Cited by 47 publications

References 1 publication

Molecular Basis of Visual Excitation

Molecular Basis of Visual Excitation

The photochemistry of vision

The Porphyropsin Visual System

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