AJP - Gastrointestinal and Liver Physiology, Vol 253, Issue 1 33-G39, Copyright © 1987 by American Physiological Society
Degradation of endogenous heptadecapeptide gastrin by endopeptidase 24.11 in the pig
D. M. Power, N. Bunnett, A. J. Turner and R. Dimaline
Hydrolysis of heptadecapeptide gastrin (G-17) by endopeptidase 24.11 (EC
3.4.24.11) was studied in vivo and in vitro in the pig. Ion exchange
chromatography and radioimmunoassay with three region-specific antisera
were used to identify the products of porcine G-17 degradation. Incubation
of antral extracts with pure endopeptidase 24.11 resulted in a substantial
loss of intact G-17: 80% C-terminal immunoreactivity was lost in 60 min.
This hydrolysis was completely inhibited by phosphoramidon, which is a
specific inhibitor of endopeptidase 24.11. In antral extracts G-17
accounted for greater than 95% of total C-terminal immunoreactivity,
compared with less than 60% C-terminal immunoreactivity in the gastric
venous outflow; shorter C-terminal forms comprised the major part of the
remaining immunoreactivity. After infusion of phosphoramidon, the
concentration of intact G-17 was increased, and there was a corresponding
reduction in the concentration of other C-terminal immunoreactive
fragments. We conclude that endopeptidase 24.11 degrades G-17 in vitro and
in vivo and may be responsible for the generation of C-terminal fragments
from G-17 after secretion from the porcine antral mucosa.
