title: Influence of nanoreactor environment and substrate location on the activity of horseradish peroxidase in olive oil based water-in-oil microemulsions.
abstract: Oxidative enzymatic reactions using horseradish peroxidase (HRP) were carried out in water-in-oil (w/o) microemulsions composed of olive oil/lecithin/1-propanol/water, a model biomimetic system. The substrates used (gallic acid, octyl gallate and 2,2'-azino-bis[3-ethylbenzo-thiazoline-6-sulfonic acid] (ABTS)) have different hydrophobicities and possible locations in the microemulsion system. HRP reactivity with reference to substrate hydrophobicity and structural characteristics of the microemulsions is discussed. The nature of the enzyme microenvironments was examined using dynamic light scattering (DLS), differential scanning calorimetry (DSC) and diffusion NMR (DOSY) methodologies while the location of various enzymatic substrates in the microemulsion phase was assessed by solubility measurements and by taking pressure-area isotherms of mixed monolayers of the substrates with dipalmitoyl-phosphatidylcholine (DPPC), which is a major constituent of lecithin. In contrast to the bulk aqueous phase, in the severely restricted environment of the polar domains of the microemulsion HRP reacted faster with octyl gallate, a substrate that is solubilized at the lipid interfaces. HRP was deactivated in the olive oil microemulsions within a few hours, a phenomenon that has also been observed in other microemulsion systems.
authors.affiliation: Institute of Biological Research and Biotechnology, §Theoretical and Physical Chemistry Institute, and ⊥Institute of Organic and Pharmaceutical Chemistry, National Hellenic Research Foundation , 48 Vas. Constantinou Avenue, 11635 Athens, Greece.
authors.forename: Evangelia D
authors.initials: ED
authors.lastname: Tzika
authors.forename: Maria
authors.initials: M
authors.lastname: Christoforou
authors.forename: Stergios
authors.initials: S
authors.lastname: Pispas
authors.forename: Maria
authors.initials: M
authors.lastname: Zervou
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Papadimitriou
authors.forename: Theodore G
authors.initials: TG
authors.lastname: Sotiroudis
authors.forename: Epameinondas
authors.initials: E
authors.lastname: Leontidis
authors.forename: Aristotelis
authors.initials: A
authors.lastname: Xenakis
mesh_terms: D004789:Enzyme Activation; D006735:Horseradish Peroxidase / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry* / Q000378:metabolism; D036103:Nanotechnology; D009821:Oils / Q000737:chemistry* / Q000378:metabolism; D000069463:Olive Oil; D010938:Plant Oils / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity; D014867:Water / Q000737:chemistry / Q000378:metabolism
chemical_list: D009821:Oils; D000069463:Olive Oil; D010938:Plant Oils; D014867:Water; D006735:Horseradish Peroxidase