Novel inactive and distinctively glycosylated forms of butyrylcholinesterase from chicken serum.
Three different homologues of butyrylcholinesterase (BChE) with 75-, 62-, and 54-kDa subunit size are isolated from adult chicken serum, and all show very low or zero enzyme activity. Although the active BChE from serum with a subunit size of 81 kDa forms tetramers, the 75-kDa protein is isolated as a dimer. The homology of the 75-kDa protein with active BChE is shown by immunoreactivity with BChE-specific monoclonal antibodies, by coisolation with the active BChE, and by their identical first six N-terminal amino acids. By deglycosylation of these proteins and by their differential lectin binding, we show that the active BChE is an N-glycosylated protein of the triantennary type, whereas the inactive 75-kDa protein is O-glycosylated. These data show for the first time the existence of (1) multiple inactive forms of BChE, (2) secreted inactive cholinesterases, because they are found in serum, and (3) an O-glycosylated cholinesterase. Because cholinesterases can regulate neurite growth in vitro by a nonenzymatic mechanism, these data strongly support that both inactive and active forms of BChE may be involved in noncholinergic communication, possibly depending on particular glycosylation patterns.
Weikert
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Max-Planck-Institut für Entwicklungsbiologie, Tübingen, F.R.G.
Ebert
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D000595:Amino Acid Sequence; D000818:Animals; D002091:Butyrylcholinesterase / Q000032:analysis / Q000097:blood*; D002645:Chickens; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006031:Glycosylation; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
D002091:Butyrylcholinesterase