Enzymatic Conversion of Two Geometrical Isomers into Enantiomorphs

Abstract

MUCONIC acid is an intermediate in the oxidation of certain aromatic compounds by bacteria. It is formed enzymatically by an oxidative ring cleavage from catechol¹, and is then rearranged to β-ketoadipic acid, which cannot be further degraded by the cell-free extracts. Evans, Smith, Linstead and Elvidge² studied the action of crude cell-free bacterial extracts on the three isomers of muconic acid, and found that only the cis-cis isomer could be converted to β-ketoadipic acid. They also tested the ability of extracts to attack certain lactones related to the muconic acids, and demonstrated that γ-carboxymethyl-Δ^a-butenolide could be rapidly converted to β-ketoadipic acid. On the basis of these findings they postulated the reaction sequence shown in Fig. 1.