Investigation of the preferred Mg(II)‐adenine‐nucleotide complex at the active site of ectonucleotidases in intact vascular cells using phosphorothioate analogues of ADP and ATP

Abstract

In the presence of Mg2+ the ecto-(nucleoside diphosphatase) on intact vascular endothelial or smooth muscle cells in culture selectively catabolises the PS diastereoisomer of adenosine 5''-(.alpha.-thio]diphosphate, (PS)-ADP[.alpha.S], and the ecto-(nucleoside triphosphatase) selectively catabolises the PS isomer of adenosine 5''-[.beta.-thio]triphosphate, (PR)-ATP[.beta.S], but exhibits no selectivity towards ATP[.alpha.S] isomers. In the presence of Cd2+ selectivity to ADP[.alpha.S] and to ATP[.beta.S] isomers is reversed; in the presence of Co2+, selectivity is lost. We conclude that each enzyme preferentially recognises the .LAMBDA. (screw-sense) bidentate Mg(II)-nucleotide complex at its active site.