Acetylcholinesterase Interaction with a Lipoprotein Matrix

Abstract

The nature of the components and some of the association forces in aggregated acetylcholinesterase, extracted from the electric organ of Electrophorus electricus, were mvestigated. The aggregated acetylcholinesterase (rapidly sedimenting, 70 S, and referred to as fast acetylcholinesterase) and the dissociated or "monomer" acetylcholinesterase (11.5 S and referred to as slow acetylcholinesterase) were isolated by zonal centrifugation. The fast acetylcholinesterase was further processed by gel filtration, resulting in a fast acetylcholinesterase of low specific activity and a slow acetylcholinesterase of high specific activity and a lowered sedimentation value (10.8 S). The fast acetylcholinesterase was exposed to the hydrolytic action of various enzymes (neuraminidase, hyaluronidase, alkaline phosphatase, and phospholipase A) and examined by sucrose gradient centrifugation techniques with no effect observed on the aggregation. However, phospholipases C and D and pancreatic lipase dissociated the fast acetylcholinesterase to the slow acetylcholinesterase (1 1.5 S). With phospholipase C, but not pancreatic lipase, the acetylcholinesterase was released from a matrix of ultraviolet absorbing, non-enzymatic material which remained in its aggregated form. With pancreatic lipase the matrix was also dissociated into a "monomer" species with a sedimentation value similar to that of the "monomer" acetylcholinesterase (resembling dissociation in high ionic strength). The hydrolytic action of the lipases did not alterthe sedimentation value of the "monomer)' nor its property of reversibly forming a gelatinous precipitate at pH 4.0. However, the slow acetylcholinesterase recovered from the gel column was not sensitive to the acid pH. The results indicate that the aggregated or fast acetylcholinesterase is a complex between ('monomer" and a matrix of lipoproteins which, in itself, is an aggregation of molecular species similar in sedimentation value to the "monomer" acetylcholinesterase. A model is presented. Comparison between the matrix and the receptor protein is made.

The Release and Molecular State of Mammalian Brain Acetylcholinesterase

“…wt. However, in view of the irreversible character of the aggregation, it would seem that the aggregates do not represent pure polymeric forms of the enzyme but contain at least some 'matrix', as proposed for electric eel enzyme by GRAFIUS, BOND and MILLAR (1971). The aggregation behaviour of the brain enzyme differs from that of the electric eel enzyme.…”

Guanidino compounds inhibit acetylcholinesterase and butyrylcholinesterase activities: Effect neuroprotector of vitamins E plus C

“…3.1.1.8). AChE has been described to contribute to the integrity and permeability of the synaptic membrane during neurotransmission and conduction (Grafius et al, 1971). This enzyme has been implicated in cholinergic and non‐cholinergic actions, which may play a role in neurodegenerative diseases (Henderson et al, 1996; Cummings, 2000; Arendt et al, 1992).…”

Heterogeneity of Human Erythrocyte Acetylcholinesterase. Individual Variation Revealed by DEAE-Cellulose Chromatography and Polyacrylamide Gel Disc Electrophoresis

“…The integrity of this associa tion is probably disturbed by chromatography. Grafius et al [13] presented evidence for AChE from Electrophorus electricus being present as hetero genic subunits attached to a membrane lipoprotein. This same group of workers [10][11][12] also demonstrated a reversible aggregation of AChE con trolled by the ionic strength of the media.…”

“…There is also evidence that membrane-bound acetylcholinesterase (AChE) from other tissues exists in different polydisperse states which can easily form aggregates and interact with other membrane proteins [10][11][12][13], If this is the case, one may expect that the expression of the heterogeneity (as demonstrated by separation techniques) might vary in samples from different individuals, on the basis of the variation, either in their enzyme subunits or some other membrane component interacting with the enzyme. Further more, Coates and Simpson [1] have demonstrated a genetically determined variation in EAChE isoenzymes by electrophoresis on polyacrylamide disc gel.…”