维生素Vitamin

维生素不提供能量，也不构成组织，主要作为辅酶或辅酶前体参与代谢：B₁（硫胺素）形成焦磷酸硫胺素参与脱羧；B₂（核黄素）构成 FAD、FMN；B₃（烟酸）构成 NAD⁺、NADP⁺；B₅ 构成辅酶 A；B₆ 参与氨基酸代谢；叶酸和 B₁₂ 参与一碳单位转移和 DNA 合成。维生素 C 是抗氧化剂并参与胶原蛋白合成中的脯氨酸羟化；维生素 D 调节钙磷代谢；维生素 K 参与凝血因子的 γ-羧化。

Vitamins provide no energy and do not build tissue; most act as coenzymes or their precursors. B₁ (thiamine) forms thiamine pyrophosphate for decarboxylations, B₂ (riboflavin) forms FAD and FMN, B₃ (niacin) forms NAD⁺ and NADP⁺, B₅ forms coenzyme A, B₆ serves amino-acid metabolism, and folate and B₁₂ carry one-carbon units for DNA synthesis. Vitamin C is an antioxidant and needed for proline hydroxylation in collagen; vitamin D regulates calcium and phosphate; vitamin K is required for γ-carboxylation of clotting factors.

1747 年林德在船员中进行对照试验，证明柑橘能治疗坏血病。1897 年艾克曼发现吃糙米的鸡不患脚气病。1912 年波兰化学家冯克提出 vitamine 一词（“生命必需的胺”），后因并非都是胺而去掉末尾的 e。1928–1933 年圣捷尔吉分离出维生素 C 并由哈沃斯确定结构，两人分别获 1937 年诺贝尔生理学或医学奖和化学奖。霍奇金用 X 射线测定维生素 B₁₂ 结构，获 1964 年诺贝尔化学奖。

In 1747 Lind ran a controlled trial among sailors showing citrus fruit cures scurvy. In 1897 Eijkman found that chickens fed unpolished rice did not get beriberi. In 1912 the Polish chemist Casimir Funk coined vitamine, 'vital amine'; the final e was dropped when not all proved to be amines. Szent-Györgyi isolated vitamin C between 1928 and 1933 and Haworth determined its structure; they received the 1937 Nobel Prizes in Physiology or Medicine and Chemistry respectively. Dorothy Hodgkin solved the structure of vitamin B₁₂ by X-ray crystallography and won the 1964 Nobel Prize in Chemistry.

典型缺乏症有：维生素 A 缺乏致夜盲症，D 缺乏致佝偻病，C 缺乏致坏血病，B₁ 缺乏致脚气病，烟酸缺乏致癞皮病，叶酸缺乏与胎儿神经管缺陷相关，B₁₂ 缺乏致恶性贫血。脂溶性维生素可在体内蓄积，长期大剂量服用维生素 A、D 可能中毒；水溶性维生素多余部分一般随尿排出。

Classic deficiencies are night blindness (A), rickets (D), scurvy (C), beriberi (B₁), pellagra (niacin), neural-tube defects linked to low folate, and pernicious anaemia (B₁₂). Fat-soluble vitamins can accumulate, so long-term high doses of A or D may be toxic, while excess water-soluble vitamins are usually excreted in urine.