Structural analysis of peroxidase from the palm tree Chamaerops excelsa

The diversification of energy production through the use of renewable resources is a major goal of the contemporary society. Although Brazil has exponent advances in ethanol production, the utilization of residual lignocellulosic biomass could ensure better energy efficiency within the second-generation ethanol production. As part of the biomass composition, lignin is the most recalcitrant substance for biochemical conversion to biofuels, and it cleavage require synergistic action of various ligninolytic enzymes, including those with high redox potential ligninolytic: oxidases, peroxidases and laccases. Peroxidases are involved in several physiological processes and many biotechnological applications, since they are able to oxidize a broad variety of organic and inorganic substrates. This group of enzymes, especially those from palm trees, is known to be very stable enzymes. To date, the structural and molecular reasons for such biochemical behavior have not been extensively explored. In order to identify the structural characteristics accountable for the high stability of palm tree peroxidases, we solved and refined X-ray structure of native peroxidase from the Chamaerops excelsa (CEP). The structure revealed important modifications of the amino acid residues in the vicinity of the exposed heme edge region, involved in the substrate binding. Analysis of CEP crystallographic model also indicated the formation of a noncovalent homodimer. This dimeric arrangement results in a more stable protein quaternary structure by stabilization of the regions which are highly dynamic in other peroxidases. In addition, five N-glycosylation sites were clearly identified, which also might contribute to the enzyme stability and resistance toward proteolytic attacks.