Compound as reactive (1)

H₂O + (S)-(+)-allantoin → H⁺ + allantoate

Compound as product (2)

H⁺ + (S)-2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline → CO₂ + (S)-(+)-allantoin

2 H₂O + urate + oxygen → hydrogen peroxide + CO₂ + (S)-(+)-allantoin

Reversible reaction (1)

(S)-(+)-allantoin ↔ (R)-(-)-allantoin