Site-directed mutagenesis of human pancreatic secretory trypsin inhibitor.
Arg-42 or Lys-43 or Arg-44 of human pancreatic secretory trypsin inhibitor (PSTI) was replaced by Thr or Ser by site-directed mutagenesis, and the inactivation rates of the mutants after mixing with human trypsin were compared with that of the natural form. The inactivation rate decreased for one mutant (Arg-44----Ser), whereas no change was observed for another (Arg-42----Thr) and an increase was observed for a third (Lys-43----Thr). Kinetic studies on the interactions between human trypsin and synthetic peptides, comprising the regions of Phe39-Ser47 of the respective PSTI species, showed that human trypsin cleaved the Arg42-Lys43 bond preferentially to the Arg44-Gln45 bond. However, it is cleavage of the latter bond that is thought to cause inactivation of human PSTI. These results suggest that the Arg44-Gln45 bond of human PSTI is responsible for its inhibitory activity, and inactivation of human PSTI is probably caused by deletion of the dipeptide Lys43-Arg44.
Kikuchi
N
N
Shionogi Research Laboratories, Shionogi & Co., Ltd., Osaka.
Nagata
K
K
Shin
M
M
Mitsushima
K
K
Teraoka
H
H
Yoshida
N
N
D000596:Amino Acids; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008970:Molecular Weight; D009154:Mutation; D009841:Oligonucleotides / Q000494:pharmacology; D010455:Peptides / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism; D014359:Trypsin Inhibitor, Kazal Pancreatic / Q000235:genetics* / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000235:genetics*
D000596:Amino Acids; D009841:Oligonucleotides; D010455:Peptides; D014361:Trypsin Inhibitors; D014359:Trypsin Inhibitor, Kazal Pancreatic; D014357:Trypsin