AMPHIPHILIC AND HYDROPHILIC FORMS OF ACETYLCHOLINESTERASE AND BUTYRYLCHOLINESTERASE IN HUMAN BRAIN

Human brain acetylcholinesterase (AChE) and butyrylcholinesterase (BuC hE) were sequentially extracted, first with a Tris-saline buffer (S1) and then c with 1 % (w/v) Triton X-100 (S2). About 20 and 30 % of the AChE and BuChE activities were recovered in S1 and most of the remaini ng enzymes in S2. Main molecular forms of about 10.5 S and 12.0 S, G4 forms of AChE and BuChE, and smaller amounts of 4.5 S and 5.5 S forms, G1 species of AChE and BuChE, were measured in S1. Application of Tri ton X-114 phase partitioning and affinity chromatography on phenyl-aga rose to S1 revealed that 25% of the AChE and none of the BuChE molecul es displayed amphiphilic properties. Analysis of the enzyme activity r etained by the phenyl-agarose showed that G1 AChE constituted the bulk of the amphiphilic molecules released without detergent. Main G4 form s of AChE and BuChE were found in the S2 extract. Eighty and 45% of th e AChE and BuChE activities in S2 were measured in the detergent-rich phase by Triton X-114 phase partitioning. Thus, most of the AChE and a bout half of the BuChE molecules in S2 displayed amphiphilic propertie s. The main peak of BuChE, a 12.0 S form in gradients made with Triton X-100, splits into two peaks of 9.5 S and 12.5 S in Brij 96-containin g gradients. This suggests that hydrophilic G4 BuChE forms are predomi nant in S1 and that hydrophilic and amphiphilic isoforms coexist in S2 . (C) 1993 Wiley-Liss, Inc.