Peroxidase catalytic cycle of MCM-41-entrapped microperoxidase-11 as a mechanism for phenol oxidation.
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.
Araujo
Juliana C
JC
Centro Interdisciplinar de Investigação Bioquímica-CIIB Universidade de Mogi das Cruzes-UMC, Mogi das Cruzes-SPF Brazil.
Prieto
Tatiana
T
Prado
Fernanda M
FM
Trindade
Fabiane J
FJ
Nunes
Gabriel L C
GL
dos Santos
Jean G
JG
Di Mascio
Paolo
P
Castro
Francisco L
FL
Fernandes
Glauber J T
GJ
Fernandes
Valter J
VJ
Araujo
Antônio S
AS
Politi
Mário J
MJ
Brochsztain
Sergio
S
Nascimento
Otaciro R
OR
Nantes
Iseli L
IL
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*
D004800:Enzymes, Immobilized; C509968:MCM-41; D019800:Phenol; D012822:Silicon Dioxide; D010544:Peroxidases; C021799:microperoxidase