低分子量有机酸对红壤磷酸单酯酶活性的影响

EFFECTS OF LOW MOLECULAR WEIGHT ORGANIC ACIDS ON PHOSPHOMONOESTERASE ACTIVITY

采用室内模拟试验研究了低分子量有机酸(柠檬酸、草酸、苹果酸、酒石酸)对红壤磷酸单酯酶活性的影响。结果表明,低浓度有机酸(<1μmol g-1)对磷酸单酯酶活性有促进作用,且促进作用大小依次为柠檬酸≈草酸>苹果酸>酒石酸;而高浓度有机酸(>5μmol g-1)则为抑制作用,且抑制作用大小依次为柠檬酸>草酸>苹果酸>酒石酸。当体系pH趋向酶促反应最佳pH时,磷酸单酯酶活性增强;反之,当体系pH远离酶促反应最佳pH时,磷酸单酯酶活性减弱。有机酸根一方面通过羧基的辅助作用提高磷酸单酯酶活性;另一方面通过释放土壤A l3+、Fe3+等金属离子,对土壤磷酸单酯酶活性有一定的抑制作用。

Effects of low molecular weight organic acids on phosphomonoesterase activity in red soil were investigated in lab. Results show that phosphomonoestcrase activity was enhanced by organic acids in low concentration （ 〈 1 μmol g^-1 ） , and the effect followed the order of citric acid ≈ oxalic acid 〉 malic acid 〉 tartaric acid, but inhibited by organic acids in high concentration （ 〉 5 μmol g^-1 ） and the effect followed the order of citric acid 〉 oxalic acid 〉 malic acid 〉 tartaric acid. On the one hand, phosphomonoesterase activity was improved when pH of the system approached to the value, where enzymic reaction was optimal, while inhibited when the pH varied the other way. On the other hand, phosphomonoesterase activity was increased by organic acidic radical via carboxyl, while inhibited by release of metal ions.