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The Journal of Immunology, Vol 143, Issue 9 2933-2938, Copyright © 1989 by American Association of Immunologists
ARTICLES |
EJ McGuire, R Kerlin, JJ Cebra and S Roth
Department of Biology, University of Pennsylvania, Philadelphia 19104.
IgA from human milk and colostrum is a substrate for a galactosyltransferase also present in milk and colostrum. The secreted IgA that serves as the best acceptor for the transferase activity is the IgA that fails to bind readily to jacalin lectin. Upon becoming galactosylated by the transferase, however, the IgA shows an increased affinity for jacalin. Glycosidase and electrophoretic results indicate that the transferred galactose is beta-linked to the alpha-chain of the IgA. The IgA:transferase activity can be purified by gel filtration and cation exchange chromatographies, as well as by affinity chromatography on Sepharose derivatized with UDP or IgM. The enzyme has an apparent Mr of about 64 kDa, is prevalent in both milk and colostrum, but has a sixfold higher sp act in colostrum.
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