7 - Chitin Metabolism in Insects

Abstract

This chapter highlights some of the recent and important findings obtained from studies conducted on the synthesis, structure, physical state, modification, organization, and degradation of chitin in insect tissues, as well as the interplay of chitin with chitin-binding proteins, the regulation of genes responsible for chitin metabolism, and, finally, the targeting of chitin metabolism for insect-control purposes. Chitin is the major polysaccharide present in insects and many other invertebrates as well as in several microbes, including fungi. It serves as the skeletal polysaccharide of several animal phyla, such as the Arthropoda, Annelida, Molluska, and Coelenterata. In several groups of fungi, chitin replaces cellulose as the structural polysaccharide. In insects, it is found in the body wall or cuticle, gut lining or peritrophic matrix (PM), salivary gland, trachea, eggshells, and muscle attachment points. In the course of evolution, insects have made excellent use of the rigidity and chemical stability of the polymeric chitin to assemble both hard and soft extracellular structures such as the cuticle (exoskeleton) and PM respectively, both of which enable insects to be protected from the environment while allowing for growth, mobility, respiration, and communication. All of these structures are primarily composites of chitin fibers and proteins with varying degrees of hydration and trace materials distributed along the structures.