Size and charge isomers of acetylcholinesterase in the cerebral cortex of young and aged rats.
Previous studies in this laboratory showed an age-related decline of acetylcholinesterase (AChE) activity in the cerebral cortex of rats. In the present study the age-related differences in enzymatic activity were evaluated in terms of individual molecular forms. Extracts containing total, soluble and membrane-bound AChE were analyzed both by ultracentrifugation in sucrose gradient and by non-denaturing gradient polyacrylamide gel electrophoresis. By ultracentrifugation two molecular forms, namely 10S and 4S (corresponding to tetrameric-G4 and monomeric-G1 forms, respectively) were separated in extracts of total and soluble AChE, while only 10S forms were present in extracts of membrane-bound AChE. Electrophoresis of soluble AChE extracts revealed slowly- and fast-migrating bands, grouped in two clusters of at least three bands each; membrane-bound AChE contained only a single slowly-migrating band. Electrophoresis of the single forms isolated by ultracentrifugation showed that slowly- and fast-migrating bands corresponded to G4 and G1 forms, respectively. Therefore, in soluble AChE no one-to-one relationship between charge- and size-isomers was observed; on the contrary, such relationship has been shown for membrane-bound AChE. This implies that soluble G4 forms and membrane-bound-G4 forms are electrophoretically different, being heterogeneous the former and homogeneous the latter. The age-related decline of total AChE, accompanied by a decrease of G4/G1 ratio, depended mainly on a decrease of membrane-bound AChE while soluble AChE and its G4/G1 ratio was unchanged. The qualitative pattern of charge isomers was not modified by aging.
Bisso
G M
GM
Laboratory of Pharmacology, Istituto Superiore di Sanità, Roma, Italy.
Briancesco
R
R
Michalek
H
H
D000110:Acetylcholinesterase / Q000737:chemistry*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D002499:Centrifugation, Density Gradient; D002540:Cerebral Cortex / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D007536:Isomerism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D000110:Acetylcholinesterase