Insights into <i>Octopus maya</i> cathepsins from metatranscriptome and genome: structure evolutionary relationships and functional role prediction in digestive processes

Physiological response to feeding is crucial for various production factors such as feed catabolism and growth. Despite growing significance in red Octopus maya aquaculture, large-scale commercial production is limited by not sufficiently knowing their nutritional needs, especially their digestive physiology. Since this species is carnivorous, one of the main feeding aspects is directed to protein digestion, but its enzymatic digestive repertoire has not been studied yet at genomic and transcriptomic levels. This study searched for protease enzymes encoded in O. maya genome and expressed in the transcriptome, allowing an initial annotation of genes involved in protein catabolism; 117 amino acid sequences related to 'octopus digestive enzymes' were retrieved from 66 available-species' genomes in the NCBI database, coding for cathepsins, papilins, and metalloproteases. Homology analysis identified 36 homologous sequences from O. maya transcriptome and three from its genome. Phylogenetic analysis grouped 37 of 39 sequences into 11 of 14 main clades, offering new insights into the evolutionary relationships and functional roles of these proteases. Phylogenetic and motif analyses resulted in selecting 19 amino acid O. maya sequences using multiple sequence alignment that were used to generate three-dimensional protein models. The obtained models revealed a diverse structural architecture among 16 modelled cathepsins; however, their catalytic potential to fully clarify their role in protein hydrolysis and cellular processes remains to be determined. Foundational data provides insights into biochemistry and physiology behind O. maya protein digestion. Further complementation of these results with enzymatic characterization of the identified proteases should allow for improved diet formulation in order to foster this species aquaculture.