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In the course of studies on colon cancer cells it was found that a few human colon carcinoma cell lines express a typical enterocytic differentiation which is characterized by the presence of brush borders and of the associated enzymes, so the current study was desinged to investigate the presence of the brush border membrane associated enzymes in normal colon, colon cancer and the possibilities that these enzymes have the oncodevelopmental nature. The results were as follows: 1. Among the brush border membrane associated enzymes, dipeptidyl aminopeptidase Ⅳ activities showed significantly higher level in the small intestine of the fetus than that of adult(p＜0.01), but other enzymes, aminopeptidase N, sucrase and trehalase revealed no statistical difference between them. 2. The level of aminopeptidase N activities in the membrane was similar to those of cytosol fraction but sucrase and trehalase were mainly present in the membrane fraction. 3. The level of brush border enzyme activities of fetal small intestine in the second trimester showed higher than those in the third trimester, but there was no difference between third trimester and adult human. 4. The sucrase activities showed highest value in the proximal third but trehalase, aminopeptidase N and dipeptidyl aminopeptidase Ⅳ in the middle third. 5. Aminopeptidase N, dipeptidyl aminopetidase Ⅳ, sucrase and trehalase were found not only in the fetal but also adult colon. 6. The brush border membrane enzymes were significantly higher level in the fetal colon than those in the adult colon. 7. The sucrase and trehalase activities in the colon cancer were significantly higher than those of adult human colon (p＜0.05). These results suggest that the brush border membrane associated enzymes, sucrase and trehalase, may have the oncodevelopmental nature in colon cancer.
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