795964.fig.001
Figure 1: L-Ascorbic acid biosynthetic pathways in plants and animals. Reactions 1–8 represent the pathway in animals and reactions 9–24 represent the pathways in plants. Enzymes in each pathway are 1, phosphoglucomutase; 2, UDP-glucose pyrophosphorylase; 3, UDP-glucose dehydrogenase; 4, glucuronate-1-phosphate uridylyltransferase; 5, glucuronate 1-kinase; 6, glucuronate reductase; 7, aldonolactonase (aka. gluconolactonase); 8, gulono-1,4-lactone oxidase or dehydrogenase; 9, glucose-6-phosphate isomerase; 10, mannose-6-phosphate isomerase; 11, phosphomannose mutase; 12, GDP-mannose pyrophosphorylase (mannose-1-phosphate guanylyltransferase) (VTC1); 13, GDP-mannose- -epimerase; 14, GDP-L-galactose phosphorylase (VTC2 and VTC5); 15, L-galactose-1-phosphate phosphatase (VTC4); 16, L-galactose dehydrogenase; 17, L-galactono-1,4-lactone dehydrogenase; 18, methylesterase; 19, D-galacturonate reductase; 20, aldonolactonase; 21, phosphodiesterase; 22, sugar phosphatase; 23, L-gulose dehydrogenase; 24, myo-inositol oxygenase. Adapted from Agius et al. [35].