摘要： 对玉米叶片磷酸烯醇丙酮酸羧化酶（PEPCase）的低温失活现象的研究结果表明，低温贮存期间，玉米叶片离体PEPCase活性随贮存时间的延长而明显降低。对效应剂G6p、Gly和2.4—D的敏感性也减弱。甘油对低温贮存期间酶的活性和对2.4—D的敏感性均有保护效应；G6p单独存在时对酶的活性和2.4—D的敏感性均无保护效应，但同一浓度的G6p在与Gly和甘油同时作用时对酶的活性和2.4—D的敏感性均有保护效应，其保护程度优于同浓度的甘油。NaCl对PEP-Case活性有抑制作用。对酶对效应剂的敏感性影响较小。对低温贮存期间酶的活性和对效应剂的敏感性均无保护效应，并能加速酶的低温失活和对效应剂敏感性的减弱。上述试剂对低温贮存期间酶对效应剂敏感性的保护程度与对其活性的保护程度相一致，表明低温贮存期间酶对效应剂敏感性减弱与其低温失活有直接关系。

关键词: 玉米, PEP羧化酶, 低温, 敏感性, 效应剂

Abstract: Result of the research on inactivation of phosphoenolpyruvate carboxylase(PEP Case) in maize leaves at low temperature showed that with the passage of preservation time of PEPCase in maize leaves in vitro at low temperature,its activity and sensitivity to such effectors as G- 6- P.Gly and 2,4- D obviously dropped.Glyeerol (20%)could protect the PEPCase activity and sensitivity to 2,4-D.when the PEPCase was stored, in low temperature.G-6-P had no the effects alone,but when the G-6-P being in the same concentration was used with Gly and glycerol,it could protect PEPCase activity and sensitivity ro 2.4-D,and the effect was greater than that of glycerol in the same concentration.NaCl showed inhibition effect on the PEPcase activity,but had less effect on the PEPCase sensitivity to the effectors,and could not protect the activity and sensitivity to the effectors when PEPCase was preserved in low temperature.Under the conditions, the PEPCase showed inactivation and less sensitivity to the effectors.The above, reagents displayed the same protective capability for the PEPCase activity and sensitivity to the effectors in petiod of preservation in Sow temperature.This indicated that less sensitivity cf PEPCase to effectors at low temperature was related to the low-temperature inaccivation.

Key words: Maize (PEP carboxylase, Low temperature, Sensitivity, Effector