Vitamin C (ascorbate) metabolism

Vitamin C (ascorbate) is an antioxidant and a cofactor in reactions catalyzed by Cu+-dependent monooxygenases and Fe++-dependent dioxygenases. Many mammals can synthesize ascorbate de novo; humans and other primates cannot due to an evolutionarily recent mutation in the gene catalyzing the last step of the biosynthetic pathway. Reactions annotated here mediate the uptake of ascorbate and its fully oxidized form, dehydroascorbate (DHA) by cells, and the reduction of DHA and monodehydroascorbate to regenerate ascorbate (Linster and Van Schaftingen 2007).

维生素C（抗坏血酸）作为一种抗氧化剂，且在由Cu+-依赖性单加氧酶和Fe++-依赖性双加氧酶催化的反应中充当辅因子。许多哺乳动物能够从头合成抗坏血酸；然而，由于人类及其他灵长类动物在生物合成途径的最后一步催化基因中发生的一种进化上较为近期的突变，故人类和其他灵长类动物无法进行此类合成。此处标注的反应涉及细胞对抗坏血酸及其完全氧化形式，脱氢抗坏血酸（DHA）的摄取，以及将DHA和单脱氢抗坏血酸还原以再生抗坏血酸的过程（Linster 和 Van Schaftingen，2007）。