Bergamini C, Grazi E
Ital J Biochem. 1980 Jul-Aug;29(4):273-88.
The existence of a 5'-nucleotidase has been demonstrated in human blood platelets. The enzyme has a low Km (20 microM) for adenosine monophosphate. It is prevalently located on the external surface of the plasma membrane as demonstrated by the similar degradation of exogenous AMP by intact and lysed platelets. Also results of inactivation studies by means of non penetrating chemical reagents point to this conclusion. Activity is inhibited by glucosyl moieties specific lectins (e.g. Concanavalin A) with varying sensitivity in intact platelets, isolated membranes and in the solubilized form. Also micromolar concentrations of ADP inhibit the activity, possibly with a competitive pattern since this effect is much more evident at low substrate concentrations. On the basis of these results, it is suggested that this enzyme is involved in in loco adenosine production in the platelets, a process which can assume a physiological important role.
已在人血小板中证实存在5'-核苷酸酶。该酶对腺苷一磷酸的米氏常数（Km）较低（20微摩尔）。如完整血小板和裂解血小板对外源AMP的降解相似所示，该酶主要位于质膜外表面。通过非穿透性化学试剂进行的失活研究结果也指向这一结论。完整血小板、分离的膜及溶解形式中，活性受糖基特异性凝集素（如伴刀豆球蛋白A）抑制，敏感性各异。微摩尔浓度的ADP也抑制该活性，可能呈竞争性模式，因为此效应在低底物浓度时更明显。基于这些结果，提示该酶参与血小板局部腺苷生成，此过程可能具有重要生理作用。
