Secretion of a novel developmentally regulated chitinase (family 19 glycosyl hydrolase) into the perivitelline fluid of the parasitic nematode, Ascaris suum.
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.
Geng
Jinming
J
Department of Biological Sciences, The University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606-3390, USA.
Plenefisch
John
J
Komuniecki
Patricia R
PR
Komuniecki
Richard
R
D000595:Amino Acid Sequence; D000818:Animals; D017165:Ascaris suum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D017173:Caenorhabditis elegans / Q000201:enzymology / Q000235:genetics; D002688:Chitinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018507:Gene Expression Regulation, Developmental; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014817:Vitelline Membrane / Q000378:metabolism*
D015801:Helminth Proteins; D011994:Recombinant Proteins; C470659:As-p50 protein, Ascaris suum; D002688:Chitinases