The early development of the parasitic nematode, Ascaris suum, occurs within a highly resistant chitinous eggshell, but little is known about the chitinase responsible for hatching. Using 2D gel electrophoresis and NH2 terminal sequencing, an abundant chitinase (As-
p50) has been identified in the perivitelline fluid surrounding infective larva prior to hatching. A cDNA encoding As-
p50 was cloned, sequenced and the protein expressed in Escherichia coli. As-
p50 is a member of family 19 glycosyl hydrolases, previously identified only in plants and a few bacteria, making the characterization of As-
p50 the first family19 glycosyl hydrolase from any animal species. Homology modeling indicates that two glutamate residues (Glu119 and Glu 151) in As-
p50 are spatially aligned with the two conserved glutamate signature residues in the Hordeum vulgare structure, confirming the assignment of As-
p50 to family19. As-
p50 statement was developmentally regulated. As-
p50 mRNA appeared between days 5 and 8 of early embryonic development prior to the formation of the first-stage larva (L1). As-
p50 protein and its associated chitinase activity began to appear between days 8 and 15 of embryonic development and remained at near constant levels until hatching. To further characterize the statement and secretion of these novel chitinases, GFP-putative promoter constructs of C08B6.4, the most closely related Caenorhabditis elegans As-
p50 homologue, were transiently expressed in C. elegans. C08B6.4 was expressed in hypodermal cells of three-fold stage larva and hatched L1s with a timing similar to that of As-
p50 and the GFP fusion protein appeared to be secreted into the space between the hypodermis and the cuticle. C08B6.4 also was expressed in four anterior amphidial neurons in all stages and the GFP-fusion protein appeared to be secreted and accumulated within the pharynx. Taken together, these results suggest that this novel chitinase may be involved in the formation of the L1 cuticle and/or the initial molt. However, it may be multifunctional and also responsible for the digestion of the eggshell during hatching, or involved in fungal resistance, as observed for its plant homologues.