| Abstract: | Maleylacetoacetate cis-trans isomerase together with glutathione has been found to isomerize cis-trans isomers of monomethyl muconate. Isomerization about a single double bond and concerted double isomerization of the diene unit occurs. In addition to the variations in substrate structure previously identified the current results demonstrate that a cis,cis diene skeleton and a conjugated ester function are accepted by the enzyme. The present work and the fiding of trans,trans-muconic acid in the urine of benzene-fed mice (16.] Xenobiotica 15, 211) suggest that maleylacetoacetate cis-trans isomerase may be responsible for the geometrical isomerization. However, cis,cis-muconaldehydic acid rather than cis,cis-muconic acid is suggested to be the early intermediate in benzene metabolism capable of rapid enzyme-catalyzed cis-trans isomerization. |
