title: Structural characterization of two papaya chitinases, a family GH19 of glycosyl hydrolases.
abstract: Two chitinases, able to use tetra-N-acetylglucosamine, chitin and chitosan as substrates, were characterized after purification from Carica papaya latex. The complete amino acid sequence of the major form and about 40% of the minor one were determined through proteolytic digestions and mass spectroscopy analysis. Sequencing demonstrated that both papaya chitinases are members of the family 19 of glycosyl hydrolases (GH19). Based on the known 3-D structures of other members of family GH19, it was expected that papaya chitinases would adopt all-alpha structures. However, circular dichroism and infrared spectroscopy indicated, for the papaya chitinases, a content of 15-20% of extended structures besides the expected 40% of alpha helices. Since the fully sequenced papaya chitinase contains a large number of proline residues the possibility that papaya chitinase contains polyproline II stretches was examined in the context of their resistance against proteolytic degradation.
authors.affiliation: Laboratoire de Chimie Générale (CP: 206/4), Institut de Pharmacie, Université Libre de Bruxelles, Campus de la Plaine, Boulevard du Triomphe, 1050, Bruxelles, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Huet
authors.forename: J
authors.initials: J
authors.lastname: Wyckmans
authors.forename: R
authors.initials: R
authors.lastname: Wintjens
authors.forename: P
authors.initials: P
authors.lastname: Boussard
authors.forename: V
authors.initials: V
authors.lastname: Raussens
authors.forename: G
authors.initials: G
authors.lastname: Vandenbussche
authors.forename: J M
authors.initials: JM
authors.lastname: Ruysschaert
authors.forename: M
authors.initials: M
authors.lastname: Azarkan
authors.forename: Y
authors.initials: Y
authors.lastname: Looze
mesh_terms: D000595:Amino Acid Sequence; D029441:Carica / Q000737:chemistry*; D002688:Chitinases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D002942:Circular Dichroism; D010450:Endopeptidases / Q000737:chemistry; D005453:Fluorescence; D006867:Hydrolases / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D013055:Spectrophotometry, Infrared
chemical_list: D006867:Hydrolases; D002688:Chitinases; D010450:Endopeptidases; D010447:Peptide Hydrolases