Fig. 1

The metabolic pathway of the glutathione biosynthesis via l-Ser, l-Cys and Gly biosynthesis in S. cerevisiae. First, 3-phospho-glycerate (3PG) dehydrogenase encoded by SER3 and SER33 converts 3PG to 3-phospho-hydroxypyruvate (3PHP) using the oxidized form of nicotinamide adenine dinucleotide (NAD⁺) as a cofactor. Second, 3-phosphoserine aminotransferase encoded by SER1 transfers an amino group from l-Glu to the 2-oxo group of 3PHP and produces l-O-phosphoserine (LPS) and 2-oxoglutarate (2OG). Finally, phosphoserine phosphatase encoded by SER2 dephosphorylates LPS to l-Ser. The produced l-Ser is further metabolized to l-Cys and Gly by cystathionine β-synthase encoded by CYS4 and serine hydroxymethyltransferase encoded by SHM2, respectively. Other abbreviations are as follows, 5,10-CH₂-THF: (6R)-5,10-methylenetetrahydrofolate; ADP: adenosine diphosphate; ATP: adenosine triphosphate; NADH: reduced form of nicotinamide adenine dinucleotide; Pi: phosphate; H₂S: hydrogen sulfide; THF: tetrahydrofolate.