Unique Lysine-Rich Sequence on the CYT Domain of AfCDH Enhances Its Interdomain Electron Transfer and Activation of AA9 LPMOs

Abstract

Cellobiose dehydrogenase (CDH) is a biologically relevant electron donor for lytic polysaccharide monooxygenase (LPMO) in the oxidative cleavage of recalcitrant polysaccharides, so exploring the intrinsic factors affecting the electron transfer from CDH to LPMO is vital for governing the CDH-driven LPMO reaction efficiency. We previously found a unique lysine-rich sequence on the cytochrome (CYT) domain of Af CDH from Aspergillus fumigatus. Here, we comprehensively compared the functionality of Af CDH and Af CDHΔ (the lysine-rich sequencedeleted mutant) to elucidate the role and significance of the lysinerich sequence in its interdomain electron transfer (IDET) and activation of LPMOs. The results showed that the lysine-rich sequence had no influence on the dehydrogenase (DH) reductive half-reaction and the interprotein electron transfer (IPET) rate from CYT to LPMOs. However, a remarkably faster IDET rate between DH and CYT was observed in Af CDH compared to that in Af CDHΔ, especially under high pH conditions. Moreover, Af CDH was found to be more effective in driving the LPMO reactions than Af CDHΔ. Our findings demonstrated that IDET is crucial for the overall electron transfer from CDH to LPMO and the CDHdriven LPMO reaction efficiency. This work provides a feasible strategy for engineering the lysine-rich sequence on CYT to potentiate the IDET rate in other CDHs and for the activation of LPMO.

Lytic polysaccharide monooxygenase synergized with lignin-degrading enzymes for efficient lignin degradation

“…In other words, LPMO might uniquely harness the extracellular redox network with temporal and spatial precisions to specifically target lignin or carbohydrate at different stages of biomass degradation to maximize the efficiency. In the context of extracellular redox network, LPMO could be activated by direct accepting electrons from CDH 14 and some small molecular reductants like diphenols 1 and ascorbic acid 3 to carry out oxidation reactions. When activating in absence of cellulose, LPMO could produce H 2 O 2 by recruiting O 2 and accepting electron from the donors.…”

“… 3 Recent breakthroughs expanded the substrates of LPMO and discovered the oxidative activities of LPMOs on all major polysaccharides, including cellulose, 4 , 5 hemicellulose, 6 , 7 , 8 chitin, 3 , 9 and starch. 10 Current studies also suggested that LPMOs oxidized carbohydrate through recruiting oxygen to copper active site 11 , 12 , 13 and accepting electrons from a variety of external electron donors, including cellobiose dehydrogenase (CDH), 14 photosynthetic pigment, 15 and small molecular reductants. 1 , 3 , 5 , 16 , 17 Despite the progresses, it is still unclear if LPMOs oxidize the substrates beyond the carbohydrates in lignocellulose.…”