Lytic Polysaccharide Monooxygenase Participates In The Quinone Redox Cycle To Drive The Fenton Reaction

The quinone redox cycle utilizes hydroquinone/quinone compounds as electron shuttle carriers to drive the Fenton reaction,which plays an important role in the extracellular degradation of lignocellulose by wood rot fungi.Lytic Polysaccharide Monooxygenase?LPMO?is a recently discovered novel copper-dependent oxidase that oxidizes glycosidic linkages and promotes hydrolysis of polysaccharides driven by exogenous electron donors such as ascorbic acid and hydroquinone.The semiquinone intermediates produced during the LPMO oxidation of hydrazine have been shown to reduce Fe³⁺to Fe²⁺and produce H₂O₂,resulting in the Fenton reaction and the production of hydroxyl radicals.Does it mean that LPMO is likely to participate in the redox cycle to drive the Fenton reaction?For the first time,this paper links LPMO to the quinone redox cycle,and in vitro confirmed that LPMO can participate in the quinone redox cycle to drive the Fenton reaction and generate hydroxyl radicals.This paper systematically studied the formation of H₂O₂,ferric reduction and hydroxyl radical during glucose dehydrogenase?GDH?and benzoquinone reductase?BQR?synergistically with LPMO reaction.The specific research results are as follows:Through heterologous expression and purification,obtained the lytic polysaccharide monooxygenase from Iprex lacteus CD2?Il LPMO9A?and Echinodontium taxodii 2538?EtLPMO9A?,glucose dehydrogenase?GcGDH?from Glomerella cingulate and the benzoquinone reductase?PoBQR2?from Pleurotus ostreatus BP3,and carried out the bioinformatics analysis.Studies on the enzymatic properties of LPMO have shown that hydroquinone compounds such as 2-methoxy-1,4-hydroquinone?MBQH₂?and2,6-dimethoxy-1,4-hydroquinone?DBQH₂?could be used as the electron donor to drive IlLPMO9A and Et LPMO9A.Both LPMO could oxidize the cellulose substrate at the C1and C4 positions and promoted cellulose hydrolysis,and at pH 5.0 and 50°C,showed the strongest activity,the highest increase of cellulose hydrolysis rate was 28.89%and 28.41%respectively.In the systematic study of LPMO involved in quinone redox,it was found that different LPMO can promote ferric reduction in two ways:first,GcGDH provided electrons for LPMO by reducing 2,6-dimethoxy-1,4-benzoquinone?DBQ?to reduce Fe³⁺,the ferric reduction ability is enhanced 252.9%?IlLPMO9A?and 237.8%?EtLPMO9A?;second,PoBQR2 provides electron by reducing MBQ or DBQ to reduce Fe³⁺and produce H₂O₂,and the iron reduction ability is enhanced 81.9%?Il LPMO9A?and 30.4%.?EtLPMO9A?;The study also found that LPMO can participate in the quinone redox system and has a synergistic effect with PoBQR2 and GcGDH.When LPMO and GDH act synergistically,the concentration of hydroxyl radicals in the Fenton reaction increases271.6%?Il LPMO9A?and 82.9%?Et LPMO9A?respectively.When LPMO and BQR act synergistically,the concentration of hydroxyl radicals can be increased 23.4%?Il LPMO9A?.And 5.3%?Et LPMO9A?.In summary,this paper not only confirmed that LPMO reduces Fe³⁺to Fe²⁺by synergistic action with GDH or BQR,and found that LPMO participated in the quinone redox cycle,which significantly promoted the production of hydroxyl radicals by Fenton reaction.The results of the study provided a theoretical basis for the expansion of the biological functions and the new role of LPMO in biomass degradation.