The genus Streptomyces is characterized by the production of a wide variety of secondary metabolites with remarkable biological activities and broad antibiotic capabilities. The presence of an unprecedented number of genes encoding hydrolytic enzymes with industrial appeal such as epoxide hydrolases (EHs) reveals its resourceful microscopic machinery. The whole-genome sequence of Streptomyces sp. CBMAI 2042, an endophytic actinobacterium isolated from Citrus sinensis branches, was explored by genome mining, and a putative alpha/beta-epoxide hydrolase named B1EPH2 and encoded by 344 amino acids was selected for functional and structural studies. The crystal structure of B1EPH2 was obtained at a resolution of 2.2 and it was found to have a similar fold to other EHs, despite its hexameric quaternary structure, which contrasts with previously solved dimeric and monomeric EH structures. While B1EPH2 has a high sequence similarity to EHB from Mycobacterium tuberculosis, its cavity is similar to that of human EH. A group of 12 aromatic and aliphatic racemic epoxides were assayed to determine the activity of B1EPH2; remarkably, this enzyme was able to hydrolyse all the epoxides to the respective 1,2-diols, indicating a wide-range substrate scope acceptance. Moreover, the (R)- and (S)-enantiomers of styrene oxide, epichlorohydrin and 1,2-epoxybutane were used to monitor enantiopreference. Taken together, the functional and structural analyses indicate that this enzyme is an attractive biocatalyst for future biotechnological applications.
Epoxide hydrolases (EHs) are enzymes involved in the metabolism of endogenous and exogenous epoxides, and the development of EH inhibitors has important applications in the medicine. In humans, EH inhibitors are being tested in the treatment of cardiovascular diseases and show potent anti-inflammatory effects. EH inhibitors are also considerate promising molecules against infectious diseases. EHs are functionally very well studied, but only a few members have its three-dimensional structures characterized. Recently, a new EH from the filamentous fungi Trichoderma reseei (TrEH) was reported, and a series of urea or amide-based inhibitors were identified. In this study, we describe the crystallographic structures of TrEH in complex with five different urea or amide-based inhibitors with resolutions ranging from 2.6 to 1.7A. The analysis of these structures reveals the molecular basis of the inhibition of these compounds. We could also observe that these inhibitors occupy the whole extension of the active site groove and only a few conformational changes are involved. Understanding the structural basis EH interactions with different inhibitors might substantially contribute for the study of fungal metabolism and in the development of novel and more efficient antifungal drugs against pathogenic Trichoderma species.
Epoxide hydrolases (EHs) are enzymes that have high biotechnological interest for the fine and transformation industry. Several of these enzymes have enantioselectivity, which allows their application in the separation of enantiomeric mixtures of epoxide substrates. Although two different families of EHs have been described, those that have the alpha/beta-hidrolase fold are the most explored for biotechnological purpose. These enzymes are functionally very well studied, but only few members have three-dimensional structures characterised. Recently, a new EH from the filamentous fungi Trichoderma reseei (TrEH) has been discovered and functionally studied. This enzyme does not have high homology to any other EH structure and have an enatiopreference for (S)-(-) isomers. Herein we described the crystallographic structure of TrEH at 1.7A resolution, which reveals features of its tertiary structure and active site. TrEH has a similar fold to the other soluble epoxide hydrolases and has the two characteristic hydrolase and cap domains. The enzyme is predominantly monomeric in solution and has also been crystallised as a monomer in the asymmetric unit. Although the catalytic residues are conserved, several other residues of the catalytic groove are not, and might be involved in the specificity for substrates and in the enantioselectivy of this enzyme. In addition, the determination of the crystallographic structure of TrEH might contribute to the rational site direct mutagenesis to generate an even more stable enzyme with higher efficiency to be used in biotechnological purposes.
