Distribution and localization of the digestive laminarinases in animals

The presence of laminarinases in the digestive system of a number of invertebrate and vertebrate species has been investigated. The enzymes were detected in coelenterates, annelids, sipunculids, bryozoans, molluscs, arthropods (crustaceans and insects), echinoderms, tunicates and fishes. Since it could be demonstrated that, in fishes, at least, laminarinases are secreted by the intestinal mucosa rather than by associated gut bacteria, an attempt was made to correlate the distribution of these digestive enzymes with the feeding habits of the animals. The correlation is particularly evident among fishes where in the genus Leuciscus carnivores lack laminarinases in contrast to omnivores. From an evolutionary point of view, we can postulate that the possession of laminarinases is ancient in Metazoa and has been either kept or lost by more evolved taxa depending on their feeding specialization, as has already been demonstrated for chitinases and cellulases.