Structure and function of a family of chitinase isozymes from Brugian microfilariae

A family of chitinase isozymes, consisting of three proteins from the microfilariae of Brugia pahangi and two previously described chitinases from the microfilariae of B. malayi, has been characterized. The five members of this family display closely related chitin-degrading activities, characterized by strong endo- rather than exochitinase activity. All five proteins have highly conserved sequences at their amino-termini and appear to share a two-domain tertiary structure, as demonstrated by proteolysis of the native molecules. The amino-terminal domain appears to be responsible for the enzymatic activity and retains this activity when cleaved and separated from the remainder of the molecule(s). Glycosylation differences are apparent for the isozymes from the two different Brugian species. No representatives of this family could be detected in the microfilariae of another filarial species, Dirofilaria immitis, which differs in several aspects of its lifestyle from the Brugian filariae.