title: Peroxidase catalytic cycle of MCM-41-entrapped microperoxidase-11 as a mechanism for phenol oxidation.
abstract: The encapsulation of microperoxidases (MPs) into molecular sieves with controlled pore size, such as the mesoporous silica MCM-41, represents a nanotechnology strategy to control the catalytic properties of MPs and mimic the enzymatic activity of hemoproteins. In this work, the ferric microperoxidase-11 (MP-11), obtained from trypsin-catalyzed hydrolysis of horse-heart cytochrome c, was entrapped in MCM-41, thus resulting in a catalyst (Fe(III)MP11MCM41) with catalase and monooxygenase properties. The entrapment of MP-11 inside MCM-41 was confirmed by elemental analysis and UV-visible spectrum, with a red shift in the Soret band indicating that the heme group was in a hydrophobic microenvironment. Similarly to catalase, the catalyst Fe(III)MP11MCM41 exhibited specificity for hydrogen peroxide to be converted to a high-valence oxidized intermediate, Compound II. Also mimicking catalase, the cleavage of hydrogen peroxide by MP11MCM41 resulted in O2 production detected by a Clark electrode. Phenol was able to act as reducing agent of MP11MCM41 Compound II leading to the completion of a peroxidase cycle, as confirmed by UV-visible spectrometry and EPR measurements. The analysis of the reaction products by high performance liquid chromatogram coupled to tandem mass spectrometry (HPLC/MS) revealed 2,4-dihydroxyphenol as the product of phenol oxidation by MP11MCM41. Therefore, in addition to catalase activity, the catalyst MP11MCM41 also displayed monooxygenase properties, which was possible because the MP-11 heme iron promotes homolytic cleavage of the hydrogen peroxide generating hydroxyl radicals. With such characteristics, MCM-41-entrapped MP-11 is a promising catalyst for nanobiotechnological devices.
authors.affiliation: Centro Interdisciplinar de Investigação Bioquímica-CIIB Universidade de Mogi das Cruzes-UMC, Mogi das Cruzes-SPF Brazil.
authors.forename: Juliana C
authors.initials: JC
authors.lastname: Araujo
authors.forename: Tatiana
authors.initials: T
authors.lastname: Prieto
authors.forename: Fernanda M
authors.initials: FM
authors.lastname: Prado
authors.forename: Fabiane J
authors.initials: FJ
authors.lastname: Trindade
authors.forename: Gabriel L C
authors.initials: GL
authors.lastname: Nunes
authors.forename: Jean G
authors.initials: JG
authors.lastname: dos Santos
authors.forename: Paolo
authors.initials: P
authors.lastname: Di Mascio
authors.forename: Francisco L
authors.initials: FL
authors.lastname: Castro
authors.forename: Glauber J T
authors.initials: GJ
authors.lastname: Fernandes
authors.forename: Valter J
authors.initials: VJ
authors.lastname: Fernandes
authors.forename: Antônio S
authors.initials: AS
authors.lastname: Araujo
authors.forename: Mário J
authors.initials: MJ
authors.lastname: Politi
authors.forename: Sergio
authors.initials: S
authors.lastname: Brochsztain
authors.forename: Otaciro R
authors.initials: OR
authors.lastname: Nascimento
authors.forename: Iseli L
authors.initials: IL
authors.lastname: Nantes
mesh_terms: D000042:Absorption; D002384:Catalysis; D003460:Crystallization / Q000379:methods*; D004800:Enzymes, Immobilized / Q000737:chemistry; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods; D010084:Oxidation-Reduction; D010316:Particle Size; D010544:Peroxidases / Q000737:chemistry* / Q000648:ultrastructure*; D019800:Phenol / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; C509968:MCM-41; D019800:Phenol; D012822:Silicon Dioxide; D010544:Peroxidases; C021799:microperoxidase