Structural studies of Old Yellow Enzyme of Leishmania braziliensis in solution.

First described in yeast in 1932 by Christian & Warburg, the Old Yellow Enzyme (OYE) (EC 1.6.99.1) has aroused the interest of the scientific community regarding its high ability to catalyze stereoselective reactions of α/β-unsaturated carbonyl compounds with important industrial applications. In addition, the OYE family of proteins has been found in different organisms, such as plants, bacteria and protozoa, but not in mammals, which makes it an excellent candidate for a functional and molecular study aimed at more effective therapies with fewer undesirable side effects. Several OYE orthologues have been characterized; however, the real physiological role for most members of this family of proteins remains a mystery. In this paper, we present the structural studies of the OYE of Leishmania braziliensis. The findings are discussed in comparison with OYE of Trypanosoma cruzi, revealing some biophysical differences. The main differences are related to their chemical and thermal stabilities and behavior in solution. In addition, the L. braziliensis OYE shape is more elongated than that of the T. cruzi orthologue. Despite this, the active sites of these enzymes do not appear to have major differences, since their interactions with the substrate menadione occur with an affinity of the same order of magnitude, revealing that the binding sites in both proteins are essentially similar.