Corazza A, Stevanato R, Di Paolo M L, Scarpa M, Mondovì B, Rigo A
Department of Biological Chemistry, University of Padova, Italy.
Biochem Biophys Res Commun. 1992 Dec 15;189(2):722-7. doi: 10.1016/0006-291x(92)92261-u.
The system bovine plasma amine oxidase-polyamine-phosphate ion was investigated by activity measurements and 31P NMR spectroscopy. Lineweaver-Burk plots showed that phosphate ion, under physiological conditions, is an apparent competitive inhibitor of bovine plasma amine oxidase. While NMR measurements of the T1 of 31P do not suggest the binding of phosphate to/or near the paramagnetic Cu(II) sites of bovine plasma amine oxidase, the chemical shift dependence of 31P on spermidine concentration indicates the formation of a spermidine-phosphate complex. The value of the dissociation constant of this complex was found 18.5 +/- 1.4 mM, at pH 7.2, by NMR, in good agreement with the value 17.0 +/- 0.8 mM calculated from activity measurements, assuming the enzyme activity is proportional to the free amine concentration, under second order conditions. Our data suggest that the decrease of the free spermidine, due to the binding of phosphate ion, is responsible of the observed inhibition of bovine plasma amine oxidase.
通过活性测量和³¹P核磁共振光谱对牛血浆胺氧化酶-多胺-磷酸离子系统进行了研究。Lineweaver-Burk图表明，在生理条件下，磷酸离子是牛血浆胺氧化酶的一种表观竞争性抑制剂。虽然³¹P的T1的核磁共振测量结果并未表明磷酸与牛血浆胺氧化酶的顺磁性Cu(II)位点结合或在其附近，但³¹P化学位移对亚精胺浓度的依赖性表明形成了亚精胺-磷酸复合物。通过核磁共振发现在pH 7.2时该复合物的解离常数为18.5±1.4 mM，与在二阶条件下假设酶活性与游离胺浓度成正比从活性测量计算得到的17.0±0.8 mM的值非常一致。我们的数据表明，由于磷酸离子的结合导致游离亚精胺减少，这是观察到的牛血浆胺氧化酶受到抑制的原因。
