豆壳过氧化物酶的电子吸收光谱性质

Electronic Absorption Spectroscopy Properties of Soybean Hull Peroxidase

应用电子吸收光谱技术研究了豆壳过氧化物酶 ( EC1 .1 1 .1 .7)的不同氧化态电子吸收光谱 ,并与其它来源的过氧化物酶作了比较研究 .天然态酶的特征吸收峰位为 40 4 nm的 Soret带 ,638nm的α带和 50 8nm的β带 ,与过氧化氢反应可生成三类复合物 .复合物 ( Com )在 40 8、580、61 8和 655nm处出现特征吸收 ;复合物 ( Com )在 41 9、52 9和 556nm处显示特征吸收 ;复合物 ( Com )则于 41 8、543和 578nm处显示特征吸收 .天然态酶经连二亚硫酸钠还原则出现 435和 558nm的特征峰 ,与氰化钾作用在 42 2和 544nm处显示特征吸收 .氰化钾对该酶的抑制为竞争性抑制 ,其 Ki 值为 2 .4μmol/L.

The hydrogen peroxide oxidized forms of soybean hull peroxidase compounds Ⅰ,Ⅱ and Ⅲ were characterized by electronic absorption spectroscopy.The native enzyme had its Soret maximum at 404 nm and α and β bands at 638 and 508 nm.Addition of 1 molar equiv.of hydrogen peroxide to the native enzyme yielded compound Ⅰ,characterized by a Soret maximum at 408 nm with reduced intensity and by additional maxima at 580,618,and 655 nm.Addition of 2 molar equiv.of hydrogen peroxide to native SHP yielded compound Ⅱ,identified by absorption maxima at 419,529,and 556 nm.Addition of a molar excess of hydrogen peroxide to the native enzyme yielded compound Ⅲ,characterized by absorption maxima at 418,543 and 578 nm.Addition of sodium dithionite yielded the reduced form of the enzyme,characterized by absorption maxima at 435 and 558 nm.Addition of cyanide immediately changed the spectrum of native SHP and produced cyanide SHP compound,identified by absorption maxima at 422 and 544 nm.A K i of 2.4 μmol/L for competitive cyanide inhibition with respect to guaiacol was observed.