Secretion of a novel developmentally regulated chitinase (family 19 glycosyl hydrolase) into the perivitelline fluid of the parasitic nematode, Ascaris suum

• Published in: Molecular and biochemical parasitology 2002-09, Vol.124 (1), p.11-21
• Main Authors: Geng, Jinming, Plenefisch, John, Komuniecki, Patricia R, Komuniecki, Richard
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Ascaris suum; Ascaris suum - enzymology; Ascaris suum - genetics; Ascaris suum - growth & development; Caenorhabditis elegans; Caenorhabditis elegans - enzymology; Caenorhabditis elegans - genetics; Chitinase; Chitinases - chemistry; Chitinases - genetics; Chitinases - metabolism; Cloning, Molecular; Escherichia coli; Family 19 glycosyl hydrolase; Gene Expression Regulation, Developmental; Helminth Proteins - chemistry; Helminth Proteins - genetics; Helminth Proteins - metabolism; Hypodermis; Molecular Sequence Data; Nematoda; Perivitelline fluid; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Sequence Analysis, DNA; Vitelline Membrane - metabolism
• ISSN: 0166-6851; 1872-9428
• DOI: 10.1016/S0166-6851(02)00155-X

The early development of the parasitic nematode, Ascaris suum, occurs within a chitinous eggshell and an abundant chitinase (As-p50) has been identified in the perivitelline fluid (PVF) surrounding the 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 glycosyl hydrolase family 19, previously identified only in plants, making the characterization of As-p50 the first family 19 glycosyl hydrolase from any animal species. As expected, the chitinase activity of recombinant As-p50 or isolated PVF was insensitive to allosamidin. As-p50 expression was developmentally regulated. As-p50 mRNA appeared between days 5 and 8 of development prior to the formation of the first-stage larva (L1). The As-p50 protein and chitinase activity appeared later between days 8 and 15 and remained at constant levels until hatching. GFP-promoter constructs of C08B6.4, the most closely related Caenorhabditis elegans As-p50 homologue, were expressed in hypodermal cells of 3-fold stage larvae and L1s with a timing similar to that of As-p50 and the fusion protein was secreted into the space between the hypodermis and the cuticle. Taken together, these results suggest that As-p50 is involved in the formation of the L1 cuticle and/or the initial molt; however, As-p50 may be multifunctional and also responsible for the digestion of the eggshell during hatching.