兼具SOD和GPX活力的双功能酶的制备及性质研究

用苯甲基磺酰氟（ＰＭＳＦ）和Ｈ_２Ｓｅ相继处理铜锌超氧化物岐化酶（Ｃｕ，Ｚｎ－ＳＯＤ），将酶分子中的丝氨酸（Ｓｅｒ）转化为硒代半胱氨酸（ＳｅＣｙｓ），从而引入了谷胱甘肽过氧化物酶（ＧＰＸ）的催化基团，使其在ＳＯＤ酶活性大部分保留的情况下，具有ＧＰＸ活性，其ＧＰＸ活力是ＰＺ５１活力的３０倍。研究了双功能酶的最佳制备条件，包括ＰＭＳＦ的剂量、反应最适温度及Ｈ_２Ｓｅ处理时间等，并用电子能谱、ＤＴＮＢ等方法测定了双功能酶的硒含量；测定了双功能酶对不同底物的米氏常数及双功能酶的荧光光谱、紫外吸收光谱及稳定性。

Preparation and Properties of the Bifunctional Enzyme with both SOD and GPX Activities

The groups of Serinef(Ser)in superoxide dismutase(SOD) were selectively activated by phenylmethylsulfonyl fluoride (PMSF)and displaced with hydrogen selenide (H_2Se).Thus.Ser residues were mutated into selenocysteine (SeCys),which is the catalytic group of native glutathione peroxidase (GPX).Therefore,the mutated enzyme showed GPX activity and remained most of the original activity of native SOD. Its GPX activity was 30 times more than that of PZ 51. The optimal mutation conditions were established,such as PMSF concentration,reaction 52. temperature and time.The Se content of the mutated enzyme was determined by x-ray photoelectron spectrum and DTNB. Some properties of the mutated SOD,including kinetic data based on GPX activity,CD spectrum,storage stabilities etc. were also studied.