Pearce L B, Roth J A
Arch Biochem Biophys. 1983 Jul 15;224(2):464-72. doi: 10.1016/0003-9861(83)90233-3.
Complete solubilization of both the A and B forms of human brain monoamine oxidase (MAO) occurred when crude mitochondria were incubated in the presence of 50 mM octylglucoside (OG). Upon removal of this nonionic detergent by dialysis, approximately 100% of the starting activity was present in the dialysate. The effects of solubilization were examined by comparison of several properties of the membrane-bound and OG-treated oxidases. The percentage inhibition of phenylethylamine (PEA) and the 5-hydroxytryptamine (5-HT) deamination by deprenyl and clorgyline were identical. The Km values obtained for the deamination of PEA, a B-selective substrate, 5-HT, an A-selective substrate, and tyramine (TYR), a nonselective substrate, were also comparable. OG was found to inhibit type A (I50 = 8.1 mM) and B (I50 = 4.7 mM) MAO activities at concentrations at least 10-fold below those used to solubilize the oxidases. Kinetic studies revealed that OG was an apparent competitive inhibitor of PEA deamination whereas OG produced a mixed-type pattern of inhibition when 5-HT was the variable substrate. Inhibition of TYR deamination by either the A or B form of MAO produced a mixed pattern of inhibition. The findings herein suggest that solubilization of the A and B forms of MAO by OG does not significantly alter the substrate and inhibitor specificity of the oxidases following removal of detergent. However, in the presence of concentrations of OG 50 times less than the critical micellar concentration of this detergent, marked inhibition of deamination by both forms of human brain MAO is observed. Accordingly, the usefulness of OG is limited to situations where the detergent is completely removed before quantitation of MAO activity.
当粗线粒体在50 mM辛基葡糖苷（OG）存在下孵育时，人脑海单胺氧化酶（MAO）的A和B两种形式都能完全溶解。通过透析去除这种非离子去污剂后，约100%的起始活性存在于透析液中。通过比较膜结合型和经OG处理的氧化酶的几种特性，研究了溶解的效果。苯乙胺（PEA）和5-羟色胺（5-HT）脱氨反应被丙炔苯丙胺和氯吉兰的抑制百分比是相同的。对于PEA（一种B选择性底物）、5-HT（一种A选择性底物）和酪胺（TYR，一种非选择性底物）脱氨反应所获得的Km值也具有可比性。发现OG在浓度至少比用于溶解氧化酶的浓度低10倍时就能抑制A型（I50 = 8.1 mM）和B型（I50 = 4.7 mM）MAO的活性。动力学研究表明，OG是PEA脱氨反应的表观竞争性抑制剂，而当5-HT作为可变底物时，OG产生混合型抑制模式。MAO的A或B型对TYR脱氨反应的抑制产生混合型抑制模式。本文的研究结果表明，OG对MAO的A和B两种形式的溶解在去除去污剂后不会显著改变氧化酶的底物和抑制剂特异性。然而，在OG浓度比该去污剂的临界胶束浓度低50倍的情况下，观察到两种形式的人脑海MAO对脱氨反应都有明显抑制。因此，OG的用途仅限于在定量MAO活性之前完全去除去污剂的情况。
