Barker R, Boden N, Cayley G, Charlton S C, Henson R, Holmes M C, Kelly I D, Knowles P F
Biochem J. 1979 Jan 1;177(1):289-302. doi: 10.1042/bj1770289.
Benzylamine oxidase from pig plasma has been studied by a variety of chemical and physical techniques. 1. Analytical ultracentrifugation, gel electrophoresis and isoelectric-focusing studies suggest that the enzyme is composed of two subunits with closely similar primary structures. 2. E.s.r. and n.m.r. measurements show that the enzyme contains two well-separated (greater than 0.6 nm) Cu2+ ions at chemically distinct sites. Each Cu2+ ion is coordinated by two water molecules, one 'axial' and the other 'equatorial'. Both water molecules undergo fast exchange (10(5)--10(8) s-1) with solvent and are deprotonated in the pH range 8--9, but only the equatorial water molecule is displaced by the inhibitors N3- and CN-. 3. Kinetic and e.s.r. measurements show that azide and cyanide compete against O2 binding and also make the two Cu2+ sites identical. It is concluded that Cu2+ must participate in the re-oxidation of reduced enzyme by molecular O2.
已通过多种化学和物理技术对猪血浆中的苄胺氧化酶进行了研究。1. 分析超速离心、凝胶电泳和等电聚焦研究表明,该酶由两个一级结构极为相似的亚基组成。2. 电子顺磁共振(E.s.r.)和核磁共振(n.m.r.)测量结果显示,该酶在化学性质不同的位点含有两个相距甚远(大于0.6纳米)的Cu2+离子。每个Cu2+离子由两个水分子配位,一个为“轴向”水分子,另一个为“赤道面”水分子。这两个水分子均与溶剂进行快速交换(10(5)--10(8) 秒-1),并在pH值范围为8至9时发生去质子化,但只有赤道面水分子会被抑制剂N3-和CN-取代。3. 动力学和电子顺磁共振测量结果表明,叠氮化物和氰化物会与O2结合相互竞争,并且还会使两个Cu2+位点变得相同。由此得出结论,Cu2+必定参与了分子O2对还原态酶的再氧化过程。