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维生素PP(Vit.pp)缺乏可导致糙皮病。菸酸(NA)和菸酰胺(NAA)是构成Vit.PP的两种化合物,在体内NA转变成NAA才具有维生素活性。后者是组成NAD(辅酶Ⅰ)和NADP(辅酶Ⅱ)的成分。NAA除部分从食物摄入外,其余则由体内色氨酸代谢而来。色氨酸经转变为甲酰犬尿氨酸、犬尿氨酸、3—羟犬尿氨酸、3—羟邻氨基苯甲酸等的降解步骤而生成NA及NAA,称之犬尿氨酸通路。反应须有多种犬尿氨酸酶及维生素B_1、B_2和B_2辅因子参加,NAA继而合成NAD和NADP。这两种辅酶是多种脱氢酶的辅
Lack of vitamin PP (Vit.pp) can lead to pellagra. Niacin (NA) and nicotinamide (NAA) are two compounds that make up Vit.PP, which have a vitamin activity when they are converted to NAA in the body. The latter is a component of NAD (coenzyme I) and NADP (coenzyme II). NAA in addition to some from food intake, the rest from the body tryptophan metabolism. Tryptophan converted to formyl kynurenine, kynurenine, 3-hydroxy kynurenine, 3-hydroxy anthranilic acid and other degradation steps to generate NA and NAA, known as kynurenine pathway . There are several kynurenase and vitamin B_1, B_2 and B_2 cofactors to participate in the reaction. NAA then synthesizes NAD and NADP. Both coenzymes are supplements of various dehydrogenases