本文探讨了以盐为添加剂时，盐的种类、酶的种类及底物结构对酶促外消旋对羟基苯甘氨酸酯不对称水解的影响。结果表明，在所研究的17种盐中，盐酸盐及草酸盐对Novozym 435催化对羟基苯甘氨酸甲酯水解无影响，磷酸钾仅可加快反应速度，碳酸氢盐、铵盐磷酸钠、醋酸钠均既能增加反应速度又能提高对映体选择性；其中碳酸氢铵为最适添加剂，可使产物对映体选择率E值达78。添加碳酸氢铵可分别提高蛋白酶Alcalase催化该反应的反应初速度及E值1.30倍和3倍；却使蛋白酶Papain催化同一反应的反应初速度和E值下降35%及60%。以碳酸氢铵为添加剂， Novozym 435催化对羟基苯甘氨酸乙酯和丙酯的E值可由5、23分别提高至25、28。

The effects of salt additives, enzymes and substrate structure on on enzymatic hydrolysis of racemic p-hydroxyphenylglycine ester were examined systematically, when the salt was used as additive. Among seventeen sorts of salts tested, chloride salts and oxalates have slight effect on Novozym 435-catalyzed hydrolysis of racemic p-hydroxyphenylglycine methyl ester, while potassium phosphate only increased the reaction rate but did not influence enzymatic enantioselectivity. Bicarbonate salts, ammonium salts, sodium phosphate and sodium acetate all could not only markedly accelerate the reaction but also improve its enantioselectivity in comparison with the reaction without adding salts, of which ammonium bicarbonate was showed to be the best additive for the reaction (E value of 78 was achieved). When Alcalase was used as catalyst, the initial reaction rate and E value of p-hydroxyphenylglycine methyl ester hydrolysis in tert-butanol were boosted by the addition of NH4HCO3 with 30% and nearly 3-fold, respectively, as compared to the result without the salt addition into the reaction system. However, interestingly, NH4HCO3 inhibited papain-catalyzed hydrolysis of racemic p-hydroxyphenylglycine methyl ester to some extent, decreasing the initial reaction rate with 35% and E value with 60%. For the Novozym 435-catalyzed hydrolysis of racemic p-hydroxyphenylglycine ethyl ester and butyl ester, the E value of both substrates were markedly improved by adding NH4HCO3 in the same reaction system from 5 to 25 and from 23 to 28, respectively.

广东省自然科学基金(020839）