Localization of amidating enzymes (PAM) in rat gastrointestinal tract.
We studied the distribution of the two enzymes involved in post-translational C-terminal alpha-amidation of regulatory peptides in rat digestive tract, using immunocytochemical methods and in situ hybridization techniques. The enzymes were located in most of the fibers and neurons of the myenteric and submucous plexus throughout the entire digestive tract and in endocrine cells of the stomach and colon. Staining of reverse-face serial sections demonstrated that the enzymes in endocrine cells of the stomach co-localized with gastrin in the bottom of the gastric glands. Some gastrin-immunoreactive cells near the neck of the gland were negative for PAM, suggesting that amidation takes place only in the more mature cells. In the colon all cells immunoreactive for glucagon and GLP1 were also positive for peptidylglycine alpha-hydroxylating monooxygenase (PHM) but not for peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL). The absence of immunoreactivity for the amidating enzymes in endocrine cells of the small intestine, known to produce C-terminally amidated peptides, suggests the existence of other amidating enzymes.
Martínez
A
A
Department of Cytology and Histology, University of Navarra, Pamplona, Spain.
Burrell
M A
MA
Kuijk
M
M
Montuenga
L M
LM
Treston
A
A
Cuttitta
F
F
Polak
J M
JM
D000818:Animals; D003106:Colon / Q000201:enzymology* / Q000294:innervation; D004702:Endocrine Glands / Q000201:enzymology; D005934:Glucagon / Q000378:metabolism; D052216:Glucagon-Like Peptide 1; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D007421:Intestine, Small / Q000201:enzymology* / Q000294:innervation; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D009097:Multienzyme Complexes; D009412:Nerve Fibers / Q000201:enzymology; D009474:Neurons / Q000201:enzymology; D010446:Peptide Fragments / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013270:Stomach / Q000201:enzymology* / Q000294:innervation
D009097:Multienzyme Complexes; D010446:Peptide Fragments; D011498:Protein Precursors; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D006899:Mixed Function Oxygenases; C035189:peptidylglycine monooxygenase