Abstract
Antigenic determinants in human urinary kallikrein (HUK) and prokallikrein (HUPK) molecules have been investigated. The number of antigenic sites was estimated to be six per mol of HUK from the quantitative precipitin reaction with the anti-HUK antibody and four per mol of HUPK with the anti-HUPK antibody. The values for the association constants were in the order of 107 M-1. Both antibodies inhibited the enzymatic activity of HUK, and the extents of the inhibition were about 80% and 95% when Pro-Phe-Arg-MCA and kininogen were used as substrate, respectivery.
Among five peptides isolated from CNBr-cleaved S-carboxymethylated (SC) HUK, N-ter-minal peptide, lle (1)-Met (79), and the peptide, Leu (99)-Met (173), were detectable by means of enzyme immunoassay, whereas the other three peptides were undetectable.
Four highly hydrophilic regions as antigenic determinants were identified in HUK molecule by hexapeptide hydropathy analysis of the amino acid sequence of HUK, each region being comprised in the four separate peptides from CNBr-cleaved SC-HUK except C-terminal one. The simulation of three dimensional structure of HUK based on the structure of porcine pancreatic kallikrein revealed that the four regions were located at the surface of HUK molecule.
