Abstract
The known functions of folate are to support one-carbon metabolism and to serve as photoreceptors for cryptochromes and photolyases. We demonstrate that 5-methyltetrahydrofolate (5-MTHF, the predominant folate in plasma) is also a potent, near diffusion limited, scavenger of singlet oxygen and quencher of excited photosensitizers. Both pathways result in decomposition of 5-MTHF, although ascorbate can protect against this loss. In the absence of photosensitizers, 5-MTHF is directly decomposed only very slowly by UVA or UVB. Although synthetic folic acid can promote DNA damage by UVA, submicromolar 5-MTHF inhibits photosensitization-induced strand breaks. These observations suggest a new role for reduced folate in protection from ultraviolet damage and have bearing on the hypothesis that folate photodegradation influenced the evolution of human skin color.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Ascorbic Acid / pharmacology
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Chromatography, High Pressure Liquid
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DNA Breaks*
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DNA Damage / drug effects*
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DNA, Superhelical / drug effects
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DNA, Superhelical / radiation effects
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Depression, Chemical
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Folic Acid / chemical synthesis
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Folic Acid / pharmacology
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Folic Acid / physiology*
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Free Radical Scavengers / pharmacology*
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Oxidation-Reduction
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Pentetic Acid / pharmacology
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Photochemistry
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Photosensitizing Agents / antagonists & inhibitors*
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Photosensitizing Agents / pharmacology
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Pteridines / antagonists & inhibitors
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Pteridines / pharmacology
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Rose Bengal / pharmacology
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Rose Bengal / radiation effects
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Singlet Oxygen / metabolism
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Sodium Azide / pharmacology
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Superoxide Dismutase / metabolism
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Tetrahydrofolates / pharmacology*
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Ultraviolet Rays / adverse effects
Substances
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DNA, Superhelical
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Free Radical Scavengers
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Photosensitizing Agents
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Pteridines
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Tetrahydrofolates
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pterine-6-carboxylic acid
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Singlet Oxygen
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Rose Bengal
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Pentetic Acid
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Folic Acid
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Sodium Azide
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Superoxide Dismutase
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Ascorbic Acid
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5-methyltetrahydrofolate