In Silico Identification of the Laccase-Encoding Gene in the Transcriptome of the Amazon River Prawn Macrobrachium amazonicum (Heller, 1862)

Background: Macrobrachium amazonicum is an opportunistic and omnivorous species that primarily feeds on plant material. Recent studies have shown that Endo-β-1,4-glucanase and Endo-β-1,4-mannanase are expressed in the transcriptome of adult specimens, while juveniles are capable of digesting nutrients from purified cellulose in their diet. In organisms that degrade raw plant material, laccase plays a key role in oxidizing phenolic compounds found in lignin, leading to its depolymerization and increasing access to cellulose and hemicellulose microfibrils. Objective: In this study, we conducted an in silico identification and characterization of the laccase-encoding gene, as this enzyme is linked to lignin biodegradation in herbivorous crustaceans. Methods: We analyzed the transcriptomes of the hepatopancreas from adult M. amazonicum, sequenced using the Illumina HiSeq 2500 platform. Subsequently, bioinformatics analyses were conducted to predict the conserved regions and active sites associated with laccase activity. Results: A complete open reading frame (ORF) of the laccase protein was identified in all datasets, comprising 609 amino acids. The top 40 similarity hits corresponded exclusively to crustaceans such as prawns, crayfish, and crabs (86.3–51.4%), while the highest divergence was observed in relation to fungi, plants, and bacteria. Three conserved domains were detected, along with the complete set of copper-binding centers (T1Cu, T2Cu, and T3Cu). A notable variable residue was methionine, suggesting a reduced redox potential in M. amazonicum laccase. Conclusion: These findings, combined with recent reports on the nutritional requirements of M. amazonicum, contribute to a deeper understanding of the digestive physiology of this species and offer valuable insights into its ability to utilize plant fibers as energy sources.