9604265 Place Chitin is the second most abundant carbon biopolymer on earth, after cellulose, yet the full details of its metabolism in vertebrates are not well know. The goals of our proposal are to elucidate the origin of endogenous chitin digestion in vertebrates, to develop a nonradioactive based method for measuring chitin assimilation applicable to other species including man, and to determine whether such assimilation contributes a significant cost or benefit to the vertebrate ingestor. The investigation will first focus on a detailed biochemical characterization of the vertebrate enzymes involve in chitin breakdown (specifically in rainbow trout, Leach's Storm-petrel, a representative seabird, and the European Starling, a representative passerine). Each of these species have been shown to ingest natural prey high in chitin content and possess extensive gastric chitinolytic activity. However, the ability to breakdown chitin does not match with chitin utilization, since digestibilities range from near zero in the trout to nearly 59% with Leach's Storm-petrel. No evidence providing chitin assimilation efficiencies in vertebrates is currently available. The data obtained will explain this apparent discrepancy between chitinolytic enzyme activity and assimilation and perhaps explain why man does not digest chitin very efficiently.
