Nutritive value of protein from sea urchin, and its effects on intestinal leucine aminopeptidase and intestinal and hepatic gamma-glutamyltranspeptidase. Seafoods are a rich source of easily digestible protein that also provides polyunsaturated fatty acids, vitamins and minerals for human nutrition. The purpose of this study was to determine the nutritive value of diets high in protein from two species of sea urchin (Paracentrotus lividus and Echinus esculentus) as compared to a high-quality reference protein such as casein, as well as the effects of these diets on leucine aminopeptidase and gamma-glutamyltranspeptidase, intestinal and hepatic enzymes. The test was carried out on three groups of male rats fed these diets for 23 days. The result of the nutritive parameters indicated that sea urchin, Echinus esculentus, were significantly lower than the casein protein except for food intake, and the nutritive parameters of sea urchin, Paracentrotus lividus, were similar to the values obtained for casein protein except for digestibility and net protein utilization. Intestinal leucine aminopeptidase activity was significantly lower (P < 0.05) in the group fed Paracentrotus lividus as compared to the group fed casein. Intestinal gamma-glutamyltranspeptidase showed a significantly higher activity in the group fed E. esculentus than in the two other groups and the hepatic gamma-glutamyltranspeptidase activity in the groups fed the two species of sea urchin were lower. Nutritive values suggested that these marine species are a good protein source and similar to casein. The activity of the enzymes under study must have been affected by the amino acid composition of the protein.