Thiophene-2-carboxyl-CoA → 5-Oxo-4,5-dihydrothiophene-2-carboxyl-CoA<br><br>Comments:<br>The starting product for this rule appears aromatic. However, the enzyme probably stabilizes a double bond between C4 and C5. C5 is then hydroxylated to form an enol, which spontaneously tautomerizes to the keto form seen in the ending product. CoA ligation to the carboxyl group occurs prior to the reaction but is bypassed in this rule for simplification.
