Ornithine carbamoyltransferase (OCT) in the jejunal mucosa, as a reference of the liver OCT

Abstract Ornithine carbamoyltransferase (OCT) was purified from normal human liver by a modification of the method of Kalousec. The protein is homogeneous by electrophoresis in sodium dodecyl sulfate containing gels and in non-dissociating gels. The specific activity is 186 μmol · min −1 · mg −1 protein. The purification factor was approximately 365, and the net recovery 3.2%. Antibodies were prepared in rabbits directed against the purified protein. These antibodies reacted specifically with purified OCT, with a crude extract of human liver and with the partially purified enzyme of the human small intestine. Apparent K m 's of OCT in the jejunal mucosa were similar to those of the liver. Physical parameters, including heat stability and pH profile, were also similar to those of liver. These results suggest that OCT in the jejunal mucosa might be of the same genetic origin as that of the liver. In addition, the fact that OCT activities were similar in jejunal samples taken from different areas indicates that jejunal mucosa obtained by per oral biopsy may be useful in detecting OCT deficiency as an alternate to liver tissue.