Functional analysis of recombinant pancreatic secretory trypsin inhibitor protein with amino-acid substitution.
BACKGROUND
We hypothesized that mutation of the pancreatic secretory trypsin inhibitor ( PSTI) gene may promote a predisposition to pancreatitis, possibly by reducing the inhibition of trypsin activity. Based on this hypothesis, we performed a biochemical analysis of recombinant PSTI protein.


METHODS
The trypsin inhibitory activity of the recombinant protein was analyzed. The activity of PSTI protein with a point mutation of the most common type: (34)Asn (AAT)-to-Ser (AGT)(101A>G N34S: N34S) in exon 3, was compared with that of the wild type.


RESULTS
The function of N34S PSTI remained unchanged under both the usual alkaline and acidic conditions compared with the wild-type PSTI. The calcium concentration did not affect the activity of recombinant PSTI. The trypsin susceptibility of the N34S protein was not increased either.


CONCLUSIONS
Mechanisms other than the conformational change of PSTI associated with amino-acid substitution, such as abnormal splicing, may underlie the predisposition to pancreatitis in patients with the N34S mutation.
Kuwata
Kinuko
K
Department of Surgery II, Kumamoto University Medical School, 1-1-1 Honjo, Kumamoto 860-8556, Japan.
Hirota
Masahiko
M
Shimizu
Hiroyuki
H
Nakae
Masanori
M
Nishihara
Shoji
S
Takimoto
Akio
A
Mitsushima
Kenji
K
Kikuchi
Norihisa
N
Endo
Kazuaki
K
Inoue
Masayasu
M
Ogawa
Michio
M
D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D002352:Carrier Proteins; D002417:Cattle; D004195:Disease Models, Animal; D015870:Gene Expression / Q000235:genetics; D020022:Genetic Predisposition to Disease; D006133:Growth Substances / Q000235:genetics*; D006801:Humans; D066298:In Vitro Techniques; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics*; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D010195:Pancreatitis / Q000235:genetics*; D011994:Recombinant Proteins / Q000235:genetics*; D013997:Time Factors; D014359:Trypsin Inhibitor, Kazal Pancreatic / Q000235:genetics*
D002352:Carrier Proteins; D006133:Growth Substances; D036341:Intercellular Signaling Peptides and Proteins; D011994:Recombinant Proteins; C486642:SPINK1 protein, human; D014359:Trypsin Inhibitor, Kazal Pancreatic