title: Implantation Serine Proteinases heterodimerize and are critical in hatching and implantation.
abstract: BACKGROUND
  We have recently reported the expression of murine Implantation Serine Proteinase genes in pre-implantation embryos (ISP1) and uterus (ISP1 and ISP2). These proteinases belong to the S1 proteinase family and are similar to mast cell tryptases, which function as multimers.
  
  
  RESULTS
  Here, we report the purification and initial characterization of ISP1 and 2 with respect to their physico-chemical properties and physiological function. In addition to being co-expressed in uterus, we show that ISP1 and ISP2 are also co-expressed in the pre-implantation embryo. Together, they form a heterodimer with an approximate molecular weight of 63 kD. This complex is the active form of the enzyme, which we have further characterized as being trypsin-like, based on substrate and inhibitor specificities. In addition to having a role in embryo hatching and outgrowth, we demonstrate that ISP enzyme is localized to the site of embryo invasion during implantation and that its activity is important for successful implantation in vivo.
  
  
  CONCLUSIONS
  On the basis of similarities in structural, chemical, and functional properties, we suggest that this ISP enzyme complex represents the classical hatching enzyme, strypsin. Our results demonstrate a critical role for ISP in embryo hatching and implantation.
authors.affiliation: Department of Biochemistry & Molecular Biology, Faculty of Medicine, University of Calgary, Heritage Medical Research Building, Calgary AB, T2N 4N1, Canada. navsharm@ucalgary.ca <navsharm@ucalgary.ca>
authors.forename: Navneet
authors.initials: N
authors.lastname: Sharma
authors.forename: Shiying
authors.initials: S
authors.lastname: Liu
authors.forename: Lin
authors.initials: L
authors.lastname: Tang
authors.forename: Jackie
authors.initials: J
authors.lastname: Irwin
authors.forename: Guoliang
authors.initials: G
authors.lastname: Meng
authors.forename: Derrick E
authors.initials: DE
authors.lastname: Rancourt
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000201:enzymology*; D019281:Dimerization; D010064:Embryo Implantation / Q000235:genetics*; D005260:Female; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D007700:Kinetics; D051379:Mice; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D014599:Uterus / Q000201:enzymology*
chemical_list: C436412:Prss28 protein, mouse; C436409:Prss29 protein, mouse; D012697:Serine Endopeptidases