[Quaternary structure of butyrylcholinesterase from horse blood serum].

The molecular weight of butyrylcholinesterase from horse blood serum was determined using the method of analytical ultracentrifugation. The molecular weight of the enzyme subunit was also determined by its mobility in gel containing sodium dodecyl sulphate. The number of active sites was determined by titrating butyrylcholinesterase with a specific inhibitor, namely di-isopropyl phosphorofluoridate. A conclusion is made that butyrylcholinesterase is a tetramer with one active site per unit.