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以6-磷酸葡萄糖、磷酸苯二钠、β-萘酚磷酸和对硝基苯磷酸为底物,研究了L-苯丙氨酸对人胎盘碱性磷酸酶的抑制作用。结果发现,L-苯丙氨酸在不同条件下可以呈现抑制作用,也可呈现激活作用。不同类型的底物对L-苯丙氨酸的这两种相反的作用均给予显著的影响。在前三种底物条件下,当高底物浓度时,L-苯丙氨酸表现出反竞争性抑制作用;低底物浓度时,则呈现激活作用。这种激活作用随底物浓度的升高而减弱。在后一种底物条件下,低浓度的L-苯丙氨酸表现出非竞争性抑制作用;高浓度时,则表现出激活作用。底物浓度对L-苯丙氨酸的这种动力学行为无影响。本文试图对碱性磷酸酶的这种复杂动力学行为予以理论上的探讨。
The inhibitory effect of L-phenylalanine on human placental alkaline phosphatase was studied with 6-phosphoglucose, phenylbiphenyl phosphate, β-naphthol phosphate and p-nitrophenyl phosphate as substrates. The results showed that, L-phenylalanine can be inhibited under different conditions, but also showed activation. Different types of substrates have a significant effect on both opposite effects of L-phenylalanine. L-Phenylalanine exhibited anti-competitive inhibition at high substrate concentrations at the first three substrate conditions, and activation at low substrate concentrations. This activation decreases with increasing substrate concentration. In the latter substrate condition, L-phenylalanine at low concentrations showed a noncompetitive inhibitory effect; at high concentrations, L-phenylalanine showed an activating effect. Substrate concentrations have no effect on this kinetic behavior of L-phenylalanine. This article attempts to theoretically investigate this complex kinetic behavior of alkaline phosphatase.