title: Exploring the process-structure-function relationship of horseradish peroxidase through investigation of pH- and heat induced conformational changes.
abstract: Given the importance of peroxidase as an indicator for the preservation of vegetables by heat treatment, the present study is focused on enzyme behavior under different pH and temperature conditions, in terms of process-structure-function relationships. Thus, the process-structure-function relationship of peroxidase was investigated by combining fluorescence spectroscopy, in silico prediction methods and inactivation kinetic studies. The fluorescence spectra indicated that at optimum pH value, the Trp(117) residue is not located in the hydrophobic core of the protein. Significant blue- and red-shifts were obtained at different pH values, whereas the heat-treatment did not cause significant changes in Trp and Tyr environment. The ANS and quenching experiments demonstrated a more flexible conformation at lower pH and respectively at higher temperature. On the other hand molecular dynamics simulations at different temperatures highlighted that the secondary structure appeared better preserved against temperature, whereas the tertiary structure around the heme was more affected. Temperature dependent changes in the hydrogen bonding and ion paring involving amino acids from the heme-binding region (His(170) and Asp(247)) might trigger miss-coordination of the heme iron atom by His(170) residue and further enzyme activity loss.
authors.affiliation: "Dunărea de Jos" University of Galati, Faculty of Food Science and Engineering, Domnească Street 111, 800201 Galati, Romania.
authors.forename: Nicoleta
authors.initials: N
authors.lastname: Stănciuc
authors.affiliation: "Dunărea de Jos" University of Galati, Faculty of Food Science and Engineering, Domnească Street 111, 800201 Galati, Romania.
authors.forename: Iuliana
authors.initials: I
authors.lastname: Aprodu
authors.affiliation: "Dunărea de Jos" University of Galati, Faculty of Food Science and Engineering, Domnească Street 111, 800201 Galati, Romania.
authors.forename: Elena
authors.initials: E
authors.lastname: Ioniță
authors.affiliation: "Dunărea de Jos" University of Galati, Faculty of Food Science and Engineering, Domnească Street 111, 800201 Galati, Romania.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Bahrim
authors.affiliation: "Dunărea de Jos" University of Galati, Faculty of Food Science and Engineering, Domnească Street 111, 800201 Galati, Romania. Electronic address: grapeanu@ugal.ro.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Râpeanu
mesh_terms: D031215:Armoracia / Q000737:chemistry / Q000201:enzymology*; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000378:metabolism*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence
chemical_list: D006735:Horseradish Peroxidase
keywords: Conformation; Fluorescence spectroscopy; Inactivation kinetics; Molecular dynamics; Peroxidase