Cholinesterase has been bonded to Procion brilliant orange – DEAE-cellulose. The matrix-supported enzyme has a lower activity than the free enzyme in solution; thermal stability, however, is much greater. A marked difference in the Km (apparent) value of the derivatized protein was observed (substrate used was acetylcholine chloride, free Cholinesterase Km = 9.6 × 10−4 M, bound Cholinesterase Km = 1.0 × 10−2 M).