title: Susceptibility of mammalian deoxyribonucleases I (DNases I) to proteolysis by proteases and its relationships to tissue distribution: biochemical and molecular analysis of equine DNase I.
abstract: Equine (Equus caballus) deoxyribonuclease I (DNase I) was purified from the parotid gland, and its 1295-bp cDNA was cloned. The mature equine DNase I protein consisted of 260 amino acid residues. The enzymatic properties and structural aspects of the equine enzyme were closely similar to those of other mammalian DNases I. Mammalian DNases I are classified into three types--pancreatic, parotid and pancreatic-parotid-based on their tissue distribution; as equine DNase I showed the highest activity in the parotid gland, it was confirmed to be of the parotid-type. Comparison of the susceptibility of mammalian DNases I to proteolysis by proteases demonstrated a marked correlation between tissue distribution and sensitivity/resistance to proteolysis; pancreatic-type DNase I shared properties of resistance to proteolysis by trypsin and chymotrypsin, whereas parotid-type DNase I did not. In contrast, pancreatic-parotid-type DNase I exhibited resistance to proteolysis by pepsin, whereas the other enzyme types did not. However, site-directed mutagenesis analysis revealed that only a single amino acid substitution could not account for acquisition of proteolysis resistance in the mammalian DNase I family during the course of molecular evolution. These properties are compatible with adaptation of mammalian DNases I for maintaining their activity in vivo.
authors.affiliation: Division of Medical Genetics and Biochemistry, Faculty of Medical Sciences, University of Fukui, Eiheiji, Fukui 910-1193, Japan.
authors.forename: Misuzu
authors.initials: M
authors.lastname: Ueki
authors.forename: Haruo
authors.initials: H
authors.lastname: Takeshita
authors.forename: Junko
authors.initials: J
authors.lastname: Fujihara
authors.forename: Gen
authors.initials: G
authors.lastname: Ueta
authors.forename: Tamiko
authors.initials: T
authors.lastname: Nakajima
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kominato
authors.forename: Koichiro
authors.initials: K
authors.lastname: Kishi
authors.forename: Reiko
authors.initials: R
authors.lastname: Iida
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yasuda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002918:Chymotrypsin / Q000737:chemistry*; D003850:Deoxyribonuclease I / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D006736:Horses; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009928:Organ Specificity; D010179:Pancreas / Q000737:chemistry* / Q000201:enzymology; D010306:Parotid Gland / Q000737:chemistry* / Q000201:enzymology; D010802:Phylogeny; D016415:Sequence Alignment; D013045:Species Specificity; D013379:Substrate Specificity; D014357:Trypsin / Q000737:chemistry*
chemical_list: D003850:Deoxyribonuclease I; D002918:Chymotrypsin; D014357:Trypsin