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目的研究铅对人类胎盘碱性磷酸酶（ＰＬＡＰ）的作用，以探讨铅影响胎儿发育的分子机制。②方法应用分光光度法测定不同浓度Ｐｂ（ＮＯ３）２存在下的ＰＬＡＰ活力，用荧光法检测其荧光光谱的变化；用双倒数作图法确定Ｐｂ（ＮＯ３）２对该酶的抑制类型。③结果低浓度的Ｐｂ（ＮＯ３）２（＜０．５０ｍｍｏｌ／Ｌ）对酶活力无明显影响，但其内源荧光强度略有增加，发射峰位蓝移；当Ｐｂ（ＮＯ３）２的浓度为０．７５ｍｍｏｌ／Ｌ时，酶活力及其荧光强度均迅速下降；当Ｐｂ（ＮＯ３）２浓度＞０．７５ｍｍｏｌ／Ｌ时，随其浓度的增加，酶活力与其荧光强度逐渐降低，但发射峰位蓝移减少；当Ｐｂ（ＮＯ３）２浓度为１０．００ｍｍｏｌ／Ｌ时，酶活力丧失，荧光熄灭。Ｐｂ（ＮＯ３）２是ＰＬＡＰ的反竞争性抑制剂，其抑制常数为１．４０ｍｍｏｌ／Ｌ．④结论Ｐｂ（ＮＯ３）２抑制了ＰＬＡＰ的活力，并使其构象发生了改变，这可能是铅影响胎儿发育的重要分子机制之一。
Objective To study the effect of lead on human placental alkaline phosphatase (PLAP) in order to explore the molecular mechanism of lead affecting fetal development. Methods The PLAP activity in the presence of different concentrations of Pb (NO3) 2 was determined by spectrophotometry. Fluorescence was used to detect the change of PLAP fluorescence intensity. The dual-reciprocal mapping method was used to determine the inhibitory effect of Pb (NO3) 2 on this enzyme. The results showed that the concentration of Pb (NO3) 2 (<0.50mmol / L) had no significant effect on the enzyme activity, but the endogenous fluorescence intensity increased slightly and the emission peak shifted blue. When the concentration of Pb (NO3) 2 was more than 0.75mmol / L, the enzyme activity and fluorescence intensity decreased gradually with the increase of the concentration of Pb (NO3) 2, but the emission peak When the concentration of Pb (NO3) 2 was 10.00mmol / L, the enzyme activity was lost and the fluorescence went out. Pb (NO3) 2 is an anti-competitive inhibitor of PLAP with an inhibitory constant of 1.40 mmol / L. Conclusion Pb (NO3) 2 inhibits the activity of PLAP and changes its conformation, which may be one of the important molecular mechanisms that lead affects fetal development.