Order Reaction ID Reaction 1 R00007 protocatechuic acid + oxygen → 2-hydroxy-4-carboxymuconate-6-semialdehyde + H⁺ 2 R00008 2-hydroxy-4-carboxymuconate-6-semialdehyde → 2-hydroxy-4-carboxymuconate semialdehyde hemiacetal 3 R00009 2-hydroxy-4-carboxymuconate semialdehyde hemiacetal + NADP⁺ → 2-pyrone-4,6-dicarboxylate + NADPH + H⁺ 4 R00010 2-pyrone-4,6-dicarboxylate + H₂O → (1E)-4-oxobut-1-ene-1,2,4-tricarboxylate + H⁺ 5 R00011 (1E)-4-oxobut-1-ene-1,2,4-tricarboxylate → (1E,3E)-4-hydroxybuta-1,3-diene-1,2,4-tricarboxylate 6 R00012 (1E,3E)-4-hydroxybuta-1,3-diene-1,2,4-tricarboxylate + H₂O → 2-hydroxy-4-oxobutane-1,2,4-tricarboxylate 7 R00013 2-hydroxy-4-oxobutane-1,2,4-tricarboxylate → pyruvate + oxaloacetic acid 8 R00054 oxaloacetate + H⁺ → pyruvate + CO₂