Proteomic analysis of digestive enzymes along the Atlantic salmon gastrointestinal tract

Abstract

A deeper understanding of the enzymatic machinery operating in the gastrointestinal tract of Atlantic salmon (Salmo salar) can aid nutritional research and the development of future aquafeeds. Current knowledge does not fully capture the diversity of digestive enzymes, their temporal and compartmental dynamics, and how the enzymatic repertoire is shaped by the feed. Here, we present a proteomic study aimed at identifying key digestive enzymes operating in the gastrointestinal tract of seawater-adapted Atlantic salmon. We have comprehensively characterized temporal protein profiles in digesta across four gut compartments in fish fed two feeds differing in protein sources (Feed A: plant-based, and Feed B: fish meal-based). Sixty-three proteins relevant to digestive functions were detected, including 41 proteases, 14 carbohydrate-active enzymes and 8 lipases. This enzymatic landscape includes multiple isoforms of key digestive enzymes, including pepsins, trypsins, chymotrypsins, elastases, lipases and chitinases, highlighting the complexity of nutrient breakdown in Atlantic salmon. Ten mucins were also detected, potentially serving as indicators for assessing feed-related impacts on gut barrier function. Overall, the abundance of proteolytic enzymes across gastrointestinal compartments was minimally affected by the protein source suggesting a generic digestive response that is not substantially modulated by protein composition.