Enzymatic conversion of type B to O erythrocytes with Coffea (coffee bean) alpha-D-galactosidase was first described by Harpaz and Flowers and subsequently adopted by others (1,2). An enzyme-linked immunosorbent assay (ELISA) and soluble oligosaccharide substrates were used to study deantigenation of B erythrocytes with the Coffea enzyme. For the ELISA, microtiter wells were coated with B membranes and treated with enzyme under a variety of conditions, probed with primary IgM monoclonal anti-B followed by secondary anti-murine mu-chain specific alkaline phosphatase conjugate, then developed with substrate. This technique has allowed the rapid determination of enzymatic activity over a broad range of conditions; the purpose being to determine parameters for efficiently enhancing enzyme activity. Solid phase activity was then compared to activity against soluble oligosaccharide substrates. We have determined that, under the conditions tested, only moderate increases in enzyme activity against the B epitope can be achieved by modifying reaction conditions with the native Coffea enzyme.