Compound as reactive (1)

2 H⁺ + 2-hydroxy-4-oxobutane-1,2,4-tricarboxylate ← H₂O + (1E)-4-oxobut-1-ene-1,2,4-tricarboxylate

Compound as product (3)

2 H⁺ + (1Z,3Z)-4-hydroxybuta-1,3-diene-1,2,4-tricarboxylate → (1E)-4-oxobut-1-ene-1,2,4-tricarboxylate

H₂O + 2-pyrone-4,6-dicarboxylate → (1E)-4-oxobut-1-ene-1,2,4-tricarboxylate + H⁺

gallate + oxygen → 2 H⁺ + (1E)-4-oxobut-1-ene-1,2,4-tricarboxylate

Reversible reaction (1)

(1E)-4-oxobut-1-ene-1,2,4-tricarboxylate ↔ (1E,3E)-4-hydroxybuta-1,3-diene-1,2,4-tricarboxylate