2-Oxopent-4-enoic acid (2-oxopent-4-enoate) is formed by the dehydration of 4-hydroxy-2-oxopentanoate by 2-oxopent-4-enoate hydratase or by the hydrolysis of 2-hydroxymuconate semialdehyde by 2-hydroxymuconate-semialdehyde hydrolase.
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