Département de Biologie et Centre de Recherche Avancée en Génomique Environnementale, Université d'Ottawa, Ottawa, Ontario, K1N 6N5, Canada.
Curr Genomics. 2011 Aug;12(5):371-8. doi: 10.2174/138920211796429736.
Vitamin C (ascorbic acid) plays important roles as an anti-oxidant and in collagen synthesis. These important roles, and the relatively large amounts of vitamin C required daily, likely explain why most vertebrate species are able to synthesize this compound. Surprisingly, many species, such as teleost fishes, anthropoid primates, guinea pigs, as well as some bat and Passeriformes bird species, have lost the capacity to synthesize it. Here, we review the genetic bases behind the repeated losses in the ability to synthesize vitamin C as well as their implications. In all cases so far studied, the inability to synthesize vitamin C is due to mutations in the L-gulono-γ-lactone oxidase (GLO) gene which codes for the enzyme responsible for catalyzing the last step of vitamin C biosynthesis. The bias for mutations in this particular gene is likely due to the fact that losing it only affects vitamin C production. Whereas the GLO gene mutations in fish, anthropoid primates and guinea pigs are irreversible, some of the GLO pseudogenes found in bat species have been shown to be reactivated during evolution. The same phenomenon is thought to have occurred in some Passeriformes bird species. Interestingly, these GLO gene losses and reactivations are unrelated to the diet of the species involved. This suggests that losing the ability to make vitamin C is a neutral trait.
维生素 C（抗坏血酸）在抗氧化和胶原蛋白合成中发挥着重要作用。这些重要作用，以及每天需要的相对大量的维生素 C，可能解释了为什么大多数脊椎动物物种能够合成这种化合物。令人惊讶的是，许多物种，如硬骨鱼、灵长类动物、豚鼠，以及一些蝙蝠和雀形目鸟类，已经失去了合成它的能力。在这里，我们回顾了维生素 C 合成能力反复丧失的遗传基础及其意义。在迄今为止研究的所有情况下，不能合成维生素 C 是由于 L-古洛糖酸-γ-内酯氧化酶 (GLO) 基因的突变，该基因编码负责催化维生素 C 生物合成最后一步的酶。导致该特定基因发生突变的倾向可能是因为失去它只会影响维生素 C 的产生。虽然鱼类、灵长类动物和豚鼠的 GLO 基因突变是不可逆转的，但在蝙蝠物种中发现的一些 GLO 假基因已被证明在进化过程中被重新激活。据认为，一些雀形目鸟类也发生了同样的现象。有趣的是，这些 GLO 基因的丧失和重新激活与所涉及物种的饮食无关。这表明失去合成维生素 C 的能力是一种中性特征。
