ISSN:
1573-2568
Keywords:
small intestine
;
brush border membrane
;
carboxypeptidase P
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract A proline-specific carboxypeptidase (carboxypeptidase P, EC 3.4.12.-) was identified and partially characterized in the brush border membrane fraction of rat intestinal enterocytes and shown to be distinct from pancreatic proteases. The carboxypeptidase activity of isolated brush border membranes, with Z-Gly-Pro-Leu as substrate, was 43 nmol/min/mg protein representing a 16-fold purification when compared with mucosal cell homogenates. Activity was maximal in the middle region of the small intestine, and villus cells had twice the activity of crypt cells. Carboxypeptidase activity was maximal at pH 7.0, was stimulated by divalent cations, and was inhibited by metal chelating agents, suggesting that it is a metalloenzyme. The enzyme had the highest activity with synthetic peptides containing proline penultimate to the carboxy terminus. In vivopatterns of hydrolysis and absorption of amino acids from Z-Pro-Trp were examined using an intestinal perfusion technique. These studies indicate that brush border membrane carboxypeptidase may play an important role in the digestion of prolinecontaining peptides and proteins.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01536262
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