The protein acetylcholinesterase (AChE) has been isolated from the electroplax tissue of the electric eel (Electrophorus electricus) and purified by affinity chromatography.
Working with fresh tissue, the structural stability of this kind of preparation towards proteolysis
and/or autolysis has been investigated. Gel electrophoresis
of the purified enzyme, in the presence of sodium dodecylsulphate
and dithiothreitol, shows predominantly one
component at 80,000 molecular weight. However, gels run
at various times after purification demonstrate that the
80,000 polypeptide is susceptible to cleavage generating
peptides of 55,000, 28,000 and 25,000 molecular weight.
Evidence is presented to show that AChE is composed of four
identical subunits arranged as a dimer of dimers (α₂)₂. Incubation of the freshly affinity purified AChE with
trypsinis shown to mimic the cleavage of the 80,000 subunit by endogeneous protease. Sucrose gradient centrifugation of purified AChE shows it to be composed of two forms characterised by their sedimentation coefficients of
18S and 14S which upon proteolysis convert to a globular
11S form. Furthermore conversion of the 'native' molecular
forms to the globular form occurs faster than proteolytic
cleavage of the catalytic subunit. Some chemical modification of the protein is described in the last section of the thesis. The enzyme has been
labelled, by two different and complementary methods, so as to incorporate radioactive iodide¹²⁵, I. Of particular interest is the result observed with an enzymatic, lacto-peroxidase iodination of the 11S form of the enzyme which
shows that greater than 90% of the label is incorporated
into the low molecular weight components of the subunit.
The other results of the two iodination methods are described
and discussed.
Finally, an appendix describing the characterisation
of AChE via isokinetic sucrose gradients in included. / Science, Faculty of / Chemistry, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/41289 |
| Date | January 1976 |
| Creators | Morrod, Peter John |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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