Characterization of horseradish peroxidase catalytic cycle mediated by photoreducer substrates

• Grant number: 06/05715-4
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: April 01, 2007
• End date: February 28, 2009
• Field of knowledge: Biological Sciences - Biophysics
• Principal Investigator: Iseli Lourenço Nantes Cardoso
• Grantee: Vanessa Aparecida Soares
• Host Institution: Pró-Reitoria de Pesquisa, Pós-Graduação e Extensão e Assuntos Comunitários. Universidade de Mogi das Cruzes (UMC). Mogi das Cruzes , SP, Brazil

Abstract

Horseradish peroxidase (HRP) is an enzyme that exhibits the Fe(III) heme group as the catalytic center. The reaction with peroxides converts the enzyme to the high valence intermediates Compound I and II that are able to oxidize inorganic and organic molecules such as iodide, bromide, ascorbate, ferrocyanide, cytochrome C, phenols, aldehydes, the leuco form of many dyes and also the peroxides. The oxidation of these molecules by HRP high valence intermediates restore the native oxidation state of the enzyme and completes the catalytic cycle. The present project proposes to identify and to characterize photoreducer substrates able to enhance the HRP catalytic cycle rate. Two classes of substances will be investigated: thiazinic compounds represented by methylene blue (MB+) and the anti-psychotic drugs thioridazine (TR), trifluoperazine (TFP) and fluphenazine (FP) and the aromatic imides represented by N,N'-di(2-phosphonoetil)-1,4,5,8-naftalenodiimide (DPN) and N-dodecil-N'-(2-phosphonoetil)-1,4,5,8-naftalenodiimide (DMPN). During the master degree step it was done the characterization of MB+ as the HRP photoreducer substrate (submitted manuscript) and preliminary experiments with DPN. In the PhD degree step we will get advances in the investigation about MB+ and the other thiazinic compounds. In this period it will be also characterized the aromatic imides as HRP photoreducer substrates in homogeneous and heterogeneous media. These photochemical systems are interesting models for the study of HRP catalytic mechanisms and could be applied in nanotechnology to develop biosensors, biocatalysts for effluents, free radical systems to modify polymers and to produce new molecules. (AU)