Boschi-Muller S, Muller S, Van Dorsselaer A, Böck A, Branlant G
Maturation des ARN et Enzymologie Moléculaire, UMR 7567 CNRS-UHP, Faculté des Sciences, Vandoeuvre-Les-Nancy, France.
FEBS Lett. 1998 Nov 20;439(3):241-5. doi: 10.1016/s0014-5793(98)01377-5.
Replacing the essential Cys-149 by a selenocysteine into the active site of phosphorylating glyceraldehyde 3-phosphate dehydrogenase (GAPDH) from Bacillus stearothermophilus leads to a selenoGAPDH that mimics a selenoperoxidase activity. Saturation kinetics were observed with cumenyl and tert-butyl hydroperoxides, with a better catalytic efficiency for the aromatic compound. The enzymatic mechanism fits a sequential model where the formation of a ternary complex between the holoselenoenzyme, the 3-carboxy 4-nitrobenzenethiol used as the reductant and the hydroperoxide precedes product release. The fact that the selenoGAPDH is NAD-saturated supports a binding of hydroperoxide and reductant in the substrate binding site. The catalytic efficiency is similar to selenosubtilisins but remains low compared to selenoglutathione peroxidase. This is discussed in relation to what is known from the X-ray crystal structures of selenoglutathione peroxidase and GAPDHs.
将嗜热脂肪芽孢杆菌磷酸化甘油醛-3-磷酸脱氢酶（GAPDH）活性位点上的必需半胱氨酸-149替换为硒代半胱氨酸，可得到一种模拟硒代过氧化物酶活性的硒代GAPDH。对异丙苯过氧化氢和叔丁基过氧化氢观察到了饱和动力学，对芳香族化合物具有更高的催化效率。酶促机制符合一个顺序模型，即在全硒酶、用作还原剂的3-羧基-4-硝基苯硫醇和氢过氧化物之间形成三元复合物后再释放产物。硒代GAPDH被NAD饱和这一事实支持了氢过氧化物和还原剂在底物结合位点的结合。其催化效率与硒代枯草杆菌蛋白酶相似，但与硒代谷胱甘肽过氧化物酶相比仍然较低。结合从硒代谷胱甘肽过氧化物酶和GAPDH的X射线晶体结构中已知的信息对此进行了讨论。
