Issue 45, 2022

Peptide-based chemical models for lytic polysaccharide monooxygenases

Abstract

Copper(II) complexes of HPH-NH2 (L1) and HPHPY-NH2 (L2) peptides have been studied as small molecular models of lytic polysaccharide monooxygenases by pH-potentiometry and UV-vis, CD and EPR spectroscopy. The coordination properties of these ligands are fundamentally different from those of other non-protected N-terminal HXH-sequences concerning the metal binding ability of amide nitrogens. The proline units prevent the formation of fused chelates with the participation of amide nitrogens; therefore, instead of ATCUN-type {NH2,2N,Nim} coordination, dimer complexes (Cu2HxL2, where x = −1, −2, and −3 for L1 and 1, 0, and −1 for L2) are formed in equimolar systems above pH 5. Using H2O2 as the oxidant and PNPG as the activated substrate, these dimer complexes were proved to be relevant functional models of LPMOs, even at neutral pH. Although the tyrosine residue in L2 participates in the coordination at pH 7–9.6, it does not seem to play a role in the oxidation process. In the presence of H2O2, the dimer complexes partially dissociate to form mononuclear hydroperoxo complexes, which are stable for 1–2 hours in equimolar concentrations of H2O2. On the other hand, with excess H2O2 both their formation and their decomposition are faster. The decay of (hydro)peroxo complexes, after longer reaction times, results in the evolution of dioxygen bubbles and the formation of Cu(I) (probably through catalytic disproportionation). However, in the presence of PNPG, the formation of dioxygen bubbles was not observed. Therefore, we assumed that the formed Cu(I) complexes bind H2O2 and enter into a similar catalytic cycle as suggested recently for native LPMOs.

Graphical abstract: Peptide-based chemical models for lytic polysaccharide monooxygenases

Supplementary files

Article information

Article type
Paper
Submitted
30 Aug 2022
Accepted
23 Oct 2022
First published
25 Oct 2022

Dalton Trans., 2022,51, 17241-17254

Peptide-based chemical models for lytic polysaccharide monooxygenases

A. A. Hassoon, A. Szorcsik, L. Fülöp, Z. I. Papp, N. V. May and T. Gajda, Dalton Trans., 2022, 51, 17241 DOI: 10.1039/D2DT02836K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements