2-Oxopent-4-enoate derivative &rarr; Pyruvate derivative + Acetaldehyde or Ketone<br>1-Methyl-2-oxo derivative &rarr; Acetate + RH<br><br>Comments:<br>This rule is a continuation of the extradiol (<i>meta</i>) ring cleavage pathway and handles all 2-oxopent-4-enoate derivatives produced by bt0351. It includes hydration of the C4-C5 double bond (bt0021) to form a 4-hydroxy-2-oxopentanoate derivative and subsequent aldolytic cleavage (bt0043) of the C3-C4 bond to yield, in the case where C4 is unsubstituted, pyruvate and acetate derivatives. If C4 does contain a functional group, pyruvate and ketone derivatives will be formed. 5-Chloro-2-oxopent-4-enoate follows this pathway and produces pyruvate and chloroacetate, which undergoes hydrolytic dehalogenation (bt0022) to yield glycolate. This rule also handles intermediates, such as appropriate compounds with -OH on C4.