Author:
Panis Felix,Rompel Annette
Abstract
AbstractPolyphenol oxidases (PPOs) are ubiquitously distributed among plants, bacteria, fungi and animals. They catalyze the hydroxylation of monophenols (monophenolase activity) and the oxidation of o-diphenols (diphenolase activity) to o-quinones. PPOs are commonly present as an isoenzyme family. In walnut (Juglans regia), two different genes (jrPPO1 and jrPPO2) encoding PPOs have been identified. In this study, jrPPO2 was, for the first time, heterologously expressed in E. coli and characterized as a tyrosinase (TYR) by substrate scope assays and kinetic investigations, as it accepted tyramine and L-tyrosine as substrates. Moreover, the substrate acceptance and kinetic parameters (kcat and Km values) towards 16 substrates naturally present in walnut were assessed for jrPPO2 (TYR) and its isoenzyme jrPPO1 (TYR). The two isoenzymes prefer different substrates, as jrPPO1 shows a higher activity towards monophenols, whereas jrPPO2 is more active towards o-diphenols. Molecular docking studies performed herein revealed that the amino acid residue in the position of the 1st activity controller (HisB1 + 1; in jrPPO1 Asn240 and jrPPO2 Gly240) is responsible for the different enzymatic activities. Additionally, interchanging the 1st activity controller residue of the two enzymes in two mutants (jrPPO1-Asn240Gly and jrPPO2-Gly240Asn) proved that the amino acid residue located in this position allows plants to selectively target or dismiss substrates naturally present in walnut.
Publisher
Springer Science and Business Media LLC
Reference58 articles.
1. Pretzler, M. & Rompel, A. What causes the different functionality in type-III-copper enzymes?. Inorg. Chim. Acta 481, 25–31. https://doi.org/10.1016/j.ica.2017.04.041 (2018).
2. Pretzler, M., Bijelic, A. & Rompel, A. Fungal tyrosinases: why mushrooms turn brown. In Elsevier Reference Module in Chemistry, Molecular Sciences and Chemical Engineering (ed. Reedijk, J.) (Elsevier, Waltham, MA, 2015).
3. Kaintz, C., Mauracher, S. G. & Rompel, A. Type 3 copper proteins: recent advances on polyphenol oxidases. In Advances in Protein Chemistry and Structural Biology: Metal-containing Enzymes Vol. 97 (ed. Christov, C.) (Academic Press Elsevier APCSB, Amsterdam, Cambridge, 2014).
4. Rodríguez-López, J. N., Tudela, J., Varón, R., García-Carmona, F. & García-Cánovas, F. Analysis of a kinetic model for melanin biosynthesis pathway. J. Biol. Chem. 267, 3801–3810 (1992).
5. Rusu, M. E. et al. Process optimization for improved phenolic compounds recovery from walnut (Juglans regia L.) Septum: phytochemical profile and biological activities. Molecules 23, 2814. https://doi.org/10.3390/molecules23112814 (2018).
Cited by
11 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献