The guinea pig pancreas secretes a single trypsinogen isoform, which is defective in autoactivation.
OBJECTIVE
The aim of the present study was to purify and clone the trypsinogen isoforms from the guinea pig pancreas and characterize their activation properties.


METHODS
Trypsinogens from pancreatic homogenates were isolated by ecotin-affinity chromatography, followed by cation-exchange chromatography. Activation of trypsinogens was tested with enteropeptidase, cathepsin B, and trypsin. Complementary DNAs for pretrypsinogens were cloned from total RNA after reverse transcription and polymerase chain reaction amplification.


RESULTS
Purification of trypsinogens yielded a single peak with an N-terminal amino-acid sequence of LPIDD. Cloning of pretrypsinogen cDNAs revealed 2 distinct but nearly identical isoforms. At the amino acid level, the only difference between the 2 isoforms is an Ala/Ser change at position 15 within the signal peptide. Thus, both cDNA variants give rise to the same mature trypsinogen upon secretion. Guinea pig trypsinogen is readily activated by enteropeptidase and cathepsin B but exhibits essentially no autoactivation, under conditions where human cationic and anionic trypsinogens rapidly autoactivate.


CONCLUSIONS
The observations suggest that multiple trypsinogen isoforms and their ability to autoactivate are not required universally for normal digestive physiology in mammals. Furthermore, the inability of guinea pig trypsinogen to undergo autoactivation suggests that this species might be more resistant to pancreatitis than humans, where increased autoactivation of cationic trypsinogen mutants has been linked to hereditary pancreatitis.
Ozsvári
Béla
B
Department of Molecular and Cell Biology, Boston University, Goldman School of Dental Medicine, Boston, MA, USA.
Hegyi
Péter
P
Sahin-Tóth
Miklós
M
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004789:Enzyme Activation; D006168:Guinea Pigs / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D010179:Pancreas / Q000201:enzymology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014357:Trypsin / Q000378:metabolism; D014362:Trypsinogen / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D018076:DNA, Complementary; D007527:Isoenzymes; D012333:RNA, Messenger; D014362:Trypsinogen; D014357:Trypsin