Animal cellulases

Previous dogma has maintained that cellulose, ingested by xylophagous or he rbivorous animals, is digested by cellulolytic symbiotes. The first evidenc e in conflict with this contention involved the demonstration of cellulolyt ic activities in symbiote-free secreting organs (e.g., the salivary glands of termites) or defaunated guts. Following these demonstrations, possible e ndogenous cellulase components were purified from several cellulose-digesti ng invertebrates, but this research did little to change the general view c oncerning animal cellulose digestion. Thanks to recent developments in mole cular biology, the existence of cellulases of animal origin has been firmly established. To date, cellulase genes have been reported from arthropods ( insects and a crayfish) and nematodes. This paper describes and discusses t he presence and nature of endogenous cellulases in higher animals.