Purification and Properties of Maleylacetone cis-trans Isomerase from Vibrio 01

An enzyme from Vibrio 01 catalyzing cis-trans isomerization of maleylacetone has been identified and purified. The enzyme has a molecular weight of about 35,000 and appears to be a single unit. Its density is low compared to other proteins. Glutathione is specifically required as a coenzyme. Treatment of the enzyme with sodium borohydride in the presence of substrate and GSH leads to increased activity while in the absence of substrate, treatment with sodium borohydride leads to inhibition. Formation of a Schiff base intermediate between substrate and enzyme appears to be unlikely. N-Ethylmaleimide leads to inactivation of enzyme and suggests the importance of one or more thiol groups near the active site. Other inhibitors and potential inhibitors have been tested. The enzyme also isomerized maleylacetoacetate at a slightly faster rate.