Interaction of purified brush-border membrane aminopeptidase N and dipeptidyl peptidase IV with lectin-sepharose derivatives.
The glycoprotein nature of two peptidases purified from the rat intestinal brush-border membrane was examined by their interaction with several lectin-Sepharose derivatives. Aminopeptidase N (EC 3.4.11.2), which contains 20% carbohydrate by weight, was bound minimally (less than 30%) by columns of Con A-, RCAI- and WGA-Sepharose. Alternatively, a greater proportion of dipeptidyl peptidase IV (EC 3.4.14.-) was bound by these immobilized lectins with 50% of the enzyme binding to Con A-Sepharose. Treatment of both enzymes with neuraminidase enhanced the binding of aminopeptidase to RCAI-Sepharose by 4-fold but did not alter the binding patterns of dipeptidyl peptidase IV. A sequential fractionation of the two peptidases with columns of Con A- and RCAI-Sepharose gave four fractions of each enzyme with differing lectin-binding specificities. Approximately 60% of the dipeptidyl peptidase IV interacted with either one or both of the lectins while only 30% of the aminopeptidase N did so. Kinetic analysis of the four isolated fractions revealed some differences, possibly related to variations in the carbohydrate moiety. The findings confirm that these two purified rat intestinal brush-border membrane peptidases are glycoproteins and, while they share a common physiologic function and source, they apparently have very different and possibly unique asparagine-linked oligosaccharide side-chains. In addition, a considerable degree of microheterogeneity exists in the carbohydrate structure of these two enzymes.
D000626:Aminopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D018826:CD13 Antigens; D002462:Cell Membrane / Q000201:enzymology*; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000302:isolation & purification / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000201:enzymology; D007700:Kinetics; D037102:Lectins; D008871:Microvilli / Q000201:enzymology*; D011134:Polysaccharides; D051381:Rats; D012685:Sepharose / Q000031:analogs & derivatives
D037102:Lectins; D011134:Polysaccharides; D012685:Sepharose; D010450:Endopeptidases; D000626:Aminopeptidases; D018826:CD13 Antigens; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases