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. 2019 Oct 29;8(11):519. doi: 10.3390/antiox8110519

Figure 2.

Figure 2

Schematic representation of vitamin C biosynthetic pathways. Different colors indicate different pathways. In grey, the myoinositol pathway; in green, the gulose pathway; in yellow, the d-mannose/l-galactose pathway; in orange, the galacturonate pathway. Represented in blue are the initial steps leading to GDP-d-mannose, which is a common precursor to the d-mannose/l-galactose and gulose pathways. A question mark indicates enzymes not identified in plants (more details are provided in the text). Abbreviations: AL, aldono lactonase; GalUR, d-galacturonate reductase; GDH, l-galactose dehydrogenase; GGP, GDP-l-galactose-phosphorylase; GGulP, GDP-l-gulose pyrophosphatase; GLDH, l-galactono-1,4-lactone dehydrogenase; GluUR, glucuronate reductase; GME, GDP-d-mannose epimerase; GMP, GDP-d-mannose pyrophosphorylase; GPP, l-galactose-1-phosphate phosphatase; GulDH, l-gulose dehydrogenase; GulPP, l-gulose-1-phosphate phosphatase; GulLO, gulonolactone oxidase; MIOX, myoinositol oxygenase; PGI, phosphoglucose isomerase; PME, pectin methyl esterase; PMI, phosphomannose isomerase; PMM, phosphomannose mutase.