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Molecular Forms of Acetylcholinesterase

Jean Massoulie ; Laboratoire de Neurobiologie, Ecole Normaie Superieure, 46, Rue d'Ulm, 75230 Paris Cede.r 05, France
Suzanne Bon ; Laboratoire de Neurobiologie, Ecole Normaie Superieure, 46, Rue d'Ulm, 75230 Paris Cede.r 05, France
Francois Rieger ; Laboratoire de Neurobiologie, Ecole Normaie Superieure, 46, Rue d'Ulm, 75230 Paris Cede.r 05, France
Marc Vigny ; Laboratoire de Neurobiologie, Ecole Normaie Superieure, 46, Rue d'Ulm, 75230 Paris Cede.r 05, France

Sažetak

Several molecular forms of acetylcholinesterase are obtained
from Electrophorus or Torpedo electric organs. They have been
characterized by physico-chemical methods and observed by
electron microscopy. The most complex D form is made up of a
globular »head« containing probably twelve subunits, or three
tetrameric groups of subunits, attached to a rod like tail. Two
other asymmetric forms, C and A, may be derived from it by
removal of one or two tetramers from the »head«. These forms
can ultimately be degraded by proteolytic digestion or sonication
into tetrameric and dimeric active enzymes, G and G'. No striking
difference in the catalytic properties of these forms could be
demonstrated. An analysis of their thermal denaturation suggests
· that internal breaks may exist in the polypeptide chains without
being revealed ,in catalytic or sedimentation properties of the
molecules. /':,, H=I= values demonstrate stabilizing interactions in the
more complex molecules.
Analysis of subunits by SDS polyacrylamide gel electrophoresis
shows that one main 90 000 subunit is progressively split into a
60 000 DFP-labelled chain together with smaller peptides jn the
30 000 range. No difference could be found between D and G subunit
patterns which could ibe identified to the tail component.
Comparing the molecular weight of A (one tetramer plus ta il)
and G (tetramer), one finds that the mass of the tail should be
in the 60 000-80 000 range. Recent micrographs suggest that it
consists of three strands linked to the three tetramers in the head
of D. We therefore propose a three stranded collagen like structure
for the tail. We discuss the possible physiological role of the asymmetric
structure o.f acetylcholinesterase and its implication with the
membrane association of the enzyme. Multiple forms of acetylcholinesterase are not genetically determined i,sozymes but rather represent different states of association of the active monomern.
The significance of multiple forms of acetylcholinesterase, especially
in mammals, is considered.

Ključne riječi

Hrčak ID:

196583

URI

https://hrcak.srce.hr/196583

Datum izdavanja:

3.12.1975.

Posjeta: 705 *