Biosynthesis of Pyridoxal Phosphate STEPS 3-4 OF FIGURE 25.1:TRANSAMINATION AND OXIDATION/DECARBOXYLATION 3-Hydroxy-4-phosphohydroxy-2-ketobutyrate undergoes transamination on reaction with a-ketoglutarate Occurs by usual PLP-dependent mechanism Product 4-phosphohydroxythreonine is oxidized by NAD+to give intermediate B-keto ester which undergoes concurrent decarboxylation and yields 1-amino-3-hydroxyacetone 3- phosphate STEPS 3-4 OF FIGURE 25.1: TRANSAMINATION AND OXIDATION/DECARBOXYLATION 3-Hydroxy-4-phosphohydroxy-2-ketobutyrate undergoes transamination on reaction with a-ketoglutarate ▪ Occurs by usual PLP-dependent mechanism Product 4-phosphohydroxythreonine is oxidized by NAD+ to give intermediate b-keto ester which undergoes concurrent decarboxylation and yields 1-amino-3-hydroxyacetone 3- phosphate Biosynthesis of Pyridoxal Phosphate