The toolbox for protein digestion in decapod crustaceans: a review

Abstract

AbstractPancrustacea, including both crustaceans and insects, is the most abundant and diverse clade of Animalia and occupy all types of environments. They are studied because of their ecological, agricultural, health and economic issues, some being delicatessens. Crustaceans evolved during the Cambrian, thanks to adaptations, such as macrophagy, that allowed them to prey on diverse and energy‐rich foods, which depended on complex digestive systems that drove evolution. As heterotrophs, crustaceans depend on their ability to obtain nutrients to fulfil their material, mostly carbon and energy requirements. Protein is the most important nutrient; up to 70% dry mass of a crustacean is protein. Hence, food protein is needed to obtain free amino acids to synthesize protein de novo (from scratch), because animals cannot synthesize the ten essential amino acids de novo. The ability to digest protein must have emerged early in evolution, as shown by the finding of trypsin coding genes in eubacterial genomes. Primitive organisms selectively fixed the ability to use foreign protein as a source of amino acids by synthesizing enzymes, now termed peptidases, which were capable of recognizing and hydrolysing peptide bonds in a specific region of a polypeptide chain, based on specificity for the side chains of amino acid residues in the carboxylic side of the site of cleavage. Here, we present a brief history on what and how digestive peptidases in crustaceans became known.