INTERACTION OF ASYMMETRIC AND GLOBULAR ACETYLCHOLINESTERASE SPECIES WITH GLYCOSAMINOGLYCANS

Abstract: Chicken muscle and retina, and rat muscle asymmetric acetylcholinesterase (AChE) species were bound to immobilized heparin at 0.4 M NaCl. Binding efficiency was between 50 and 80% for crude fraction I A‐forms (A1; muscle), and nearly 100% for fraction II A‐forms (A11; muscle and retina). Antibody‐affinity‐purified A1‐forms (chicken) were, however, quantitatively bound to heparin–agarose gels, whereas diisopropylfluorophosphate‐inactivated high‐salt extracts partially prevented the binding of both A1 and A11 AChE forms, thus suggesting the presence in crude A1 extracts of heparin‐like molecules interfering with the tail–heparin interaction. All bound A‐forms were progressively displaced from the heparin–agarose columns by increasing salt concentrations, with maximal release at about 0.6 M. They were also efficiently eluted by heparin solutions (1 mg/ml), other glycosaminoglycans being much less effective. Chicken globular AChE forms (G‐forms, both low‐salt‐soluble and detergent‐soluble) also bound to immobilized heparin in the absence of salt. Stepwise elution with increasing NaCl concentrations showed maximal release of G‐forms at 0.15 M, all globular forms being totally displaced from the column at 0.4 M NaCl. Heparin (1 mg/ml) had the same eluting capacity as 0.4 M NaCl, whereas other glycosaminoglycans were only marginally effective. We conclude that the molecular forms of AChE in these vertebrate species interact with heparin, at salt concentrations that are characteristic for asymmetric and globular forms. Within the A and G molecular form groups, no differences were found in the behavior of the different fractions or subtypes, provided that the enzyme samples were free of interfering molecules. If heparin affinity reflects the ability of AChE forms to interact with extracellular matrix components, not only asymmetric but also some globular enzyme forms could be bound to basal laminae under physiological ionic strength conditions. Copyright © 1990, Wiley Blackwell. All rights reserved