DEMONSTRATION OF (CA2+-MG2+)-ATPASE ACTIVITY OF THE NEURAL CELL-ADHESION MOLECULE

In this study a possible association between (Ca2+-Mg2+)-ATPase activity and the neural cell adhesion molecule, NCAM, was investigated. The effects of various detergents on ATPase activity were evaluated, and it was found that solubilization of rat brain microsomes with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, CHAPS, released a major fraction of the (Ca2+-Mg2+)-ATPase activity together with NCAM. Using different types of solid phase immunoadsorption it was shown that NCAM antibodies selectively isolated ATPase activity. Furthermore, agarose gel immunoelectrophoresis of solubilized brain microsomes followed by ATPase assay directly in the gel revealed ATPase activity associated with the NCAM immunoprecipitate. The NCAM-associated enzyme activity had a broad nucleoside triphosphate specificity and no strict selectivity for divalent cations, indicating that the enzyme probably is an ecto-ATPase. This raises a series of intriguing questions in relation to NCAM adhesive functions.