Vitamin C (including the GLO enzyme), or start with inositol and get to ascorbic acid via L-galactonic acid to L-galactonolactone. Ascorbic acid is a common enzymatic cofactor in mammals used in the synthesis of collagen, as well as a powerful reducing agent capable of rapidly scavenging a number of reactive oxygen species (ROS). Given that ascorbate has these important functions, it is surprising that the ability to synthesize this molecule has not always been conserved. In fact, anthropoid primates, "Cavia porcellus" (guinea pigs), teleost fishes, most bats, and some Passeriform birds have all independently lost the ability to internally synthesize Vitamin C
Vitamin C -Galactose reacts with the enzyme -galactose dehydrogenase, whereby the lactone ring opens and forms again but with between the carbonyl on C1 and hydroxyl group on the C4, resulting in -galactonolactone. -Galactonolactone then reacts with the mitochondrial flavoenzyme -galactonolactone dehydrogenase. to produce ascorbic acid. -Ascorbic acid has a negative feedback on -galactose dehydrogenase in spinach. Ascorbic acid efflux by embryo of dicots plants is a well-established mechanism of iron reduction, and a step obligatory for iron uptake. All plants synthesize ascorbic acid. Ascorbic acid functions as a cofactor for enzymes involved in photosynthesis, synthesis of plant hormones, as an antioxidant