Abstract
This report is concerned with the colorimetric assay method of carboxypeptidase A activity in serum using carbonaphthoxy-L-phenylalanine (CNPA) as a substrate and the hydrolytic activity of CNPA in this reaction system.
1) No effect was observed with the addition of DFP, cyanide, trypsin or epsilon aminocaproic acid.
2) Activity was inhibited by dialysis against o-phenenthroline solution, and recovered with the addition of Zn+ + ions.
3) Further addition of the CPase A substrates (different from CNPA) inhibited this reaction, whereas the presence of CPase B substrates showed no effect.
4) In organs of humans and dogs, the pancreas was found as the only organ which was rich in CPase A activity, while traces of activity were observed in the kidneys.
5) The mean serum CPase A activity in 28 normal subjects was 289.2±3.8 units (range 272.0-312.4 units).
6) In almost all subjects with pancreatic cancer, and in some subjects with liver cirrhosis, chronic pancreatitis, diabetes mellitus, cholelithiasis, or chronic glomerulonehritis, a low level of serum CPase A activity was observed.
7) The serum CPase A level in a patient who had undergone a total pancreatectomy dropped rapidly, and only negligible activity was found 3 weeks after the operation, while serum levels of total protein, cholinesterase and amylase showed minor changes during the same clinical course.
8) It was observed that amylase activity and CPase A activity in serum changed inversely in experimental pancreatitis.
Moreover, this amylase activity and CPase A activity varied in inverse proportions to each other.
