Antibody recognition of epitopes on wild-type and mutant beta-(1 -> 4)-galactosyltransferase-1

The epitopes present on beta-(1-->4)-galactosyltransferase-1 (beta 4Gal-T1. ) have been explored using a panel of monoclonal antibodies (mAbs) raised a gainst the soluble form of the human enzyme. Reactivity of the antibodies w ith site-specific and truncated mutants of human beta 4Gal-T1 suggests the presence of a major immunogenic epitope cluster consisting of four epitopes within the stem region and mapping between amino acids 42 and 115. The cat alytic activity of the enzyme is increased in the presence of stem region-s pecific antibody. Two of the epitopes were further localized to a region be tween amino acids 42 and 77, sequences which are not shared with the recent ly cloned beta 4Gal-T2 and beta 4Gal-T3 enzymes. An epitope located close t o or within the catalytic domain is also identified, and the mAb to this re gion binds synergistically with antibodies to the stem region. (C) 1998 Els evier Science Ltd. All rights reserved.