Modified form of the fibrinogen Bbeta chain (des-Gln Bbeta), a potential long-lived marker of pancreatitis.
BACKGROUND
During an investigation of genetic variants of fibrinogen, we observed a novel form of the Bbeta chain, with a mass decrease of approximately 128 Da, in one of the controls. The plasma sample originated from an individual who had experienced acute pancreatitis a week earlier but whose serum amylase activity had returned to normal. We investigated the structure of the modified fibrinogen and explored its relationship to pancreatic disease.


METHODS
Fibrinogen was isolated from the plasma of 9 individuals with increased pancreatic amylase activity (114-1826 U/L) and presumed pancreatitis and from 6 control individuals with amylase activities <56 U/L. Fibrinogen (or fibrin) Bbeta chains were isolated by reversed-phase HPLC and analyzed directly by electrospray ionization mass spectrometry. Tryptic and CNBr peptide mapping and thrombin treatment pinpointed the location of the 128-Da loss in mass.


RESULTS
The acquired fibrinogen Bbeta chain modification was attributable to the loss of its C-terminal glutamine residue. Incubating purified fibrinogen with pancreatic carboxypeptidase A (CpA) produced an identical modification. The des-Gln Bbeta fibrinogen accounted for >80% of the Bbeta chains in 3 of the individuals with increased amylase but only approximately 5% of the Bbeta chains in control samples.


CONCLUSIONS
Pancreatic CpA activity is used as an index of acute pancreatic disease, but given that the circulatory half-lives of fibrinogen and CpA are approximately 4 days and only 2.5 h, respectively, measuring des-Gln Bbeta fibrinogen, the in vivo product of CpA activity, could provide clinicians with retrospective evidence of disease.
Schmidt
David
D
Molecular Pathology Laboratory, Canterbury Health Laboratories, Christchurch, New Zealand.
Brennan
Stephen O
SO
D000208:Acute Disease; D000681:Amylases / Q000097:blood; D015415:Biomarkers / Q000097:blood; D043422:Carboxypeptidases A / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005340:Fibrinogen / Q000032:analysis*; D006801:Humans; D010195:Pancreatitis / Q000175:diagnosis*; D020033:Protein Isoforms / Q000097:blood; D021241:Spectrometry, Mass, Electrospray Ionization
C115499:BBeta fibrinogen; D015415:Biomarkers; D020033:Protein Isoforms; D005340:Fibrinogen; D000681:Amylases; D043422:Carboxypeptidases A