Metaproteogenomic approaches for target discovery of auxiliary activities that act in conjunction with glycoside hydrolases in the digestome of lower termite Coptotermes gestroi

Termites are considered the smallest bioreactor in the world since these insects degrade lignocellulosic biomass with efficiency ranging from 65-90%. This effectiveness is achieved due to the repertoire of carbohydrate-active and accessory enzymes produced by termite and their symbiotic’s protists and bacteria. The lower termite Coptotermes gestroi is considered the major urban pest in Brazil and the literature highlights this specie as a reservoir for prospection of lignocellulose-active enzymes. The aim of this work was to comprehend the role of auxiliary-activity enzymes in the digestome of this termite. Worker’s RNA-polyA was target of pyrosequencing. 1.5 million reads were generated and assembled into ±80.000 unisequences. Using CAZy database, we predicted ±650 unisequences correlated with CAZymes. Among the auxiliary enzymes, some putative acetyl xylan and feruloyl esterases, laccases, glucose-dehydrogenases-(GDH) and aryl-oxidases-(AROX) were identified. Antioxidant/detoxification enzymes were identified such as superoxide dismutase-(SOD) and catalase-(CAT). We also conducted metaproteomic analysis in C. gestroi, using LC-MS/MS-Orbitrap. We identified ±110 proteins correlated with CAZymes such as GHs, CEs and AAs as well antioxidant/detoxification enzymes. Once GDHs, AROXs and SODs produce H₂O_2, which is needed for laccase activity and fenton chemistry, we evaluated the potential of termite crude extract to produce H₂O₂ and reduce Fe³⁺ . Our results showed that termite can generated up to 15 µM of H₂O₂ and reducing Fe³⁺ to Fe²⁺ at high levels after 1 hour of incubation. Here we describe insights about auxiliary mechanisms to GHs in C. gestroi and found evidences that fenton chemistry can play a role in termite digestion.