Radabaugh T R, Aposhian H V
Graduate Interdisciplinary Program in Genetics and Department of Molecular and Cellular Biology, The University of Arizona, Tucson, Arizona 85721, USA.
Chem Res Toxicol. 2000 Jan;13(1):26-30. doi: 10.1021/tx990115k.
An arsenate (As(V)) reductase has been partially purified from human liver. Its apparent molecular mass is approximately 72 kDa. The enzyme required a thiol and a heat stable cofactor for activity. The cofactor is less than 3 kDa in size. The thiol requirement can be satisfied by dithiothreitol (DTT). However, the extent of stimulation of reductase activity by glutathione, thioredoxin, or reduced lipoic acid was negligible compared to that of DTT. The heat stable cofactor does not appear to be Cu(2+), Mn(2+), Zn(2+), Mg(2+), or Ca(2+). The enzyme does not reduce monomethylarsonic acid (MMA(V)). The isolation and characterization of this enzyme demonstrates that in humans, the reduction of arsenate to arsenite is enzymatically catalyzed and is not solely the result of chemical reduction by glutathione as has been proposed in the past.
已从人肝脏中部分纯化出一种砷酸盐（As(V)）还原酶。其表观分子量约为72 kDa。该酶的活性需要一种硫醇和一种热稳定辅因子。该辅因子的大小小于3 kDa。硫醇需求可由二硫苏糖醇（DTT）满足。然而，与DTT相比，谷胱甘肽、硫氧还蛋白或还原型硫辛酸对还原酶活性的刺激程度可忽略不计。热稳定辅因子似乎不是铜（Cu(2+)）、锰（Mn(2+)）、锌（Zn(2+)）、镁（Mg(2+)）或钙（Ca(2+)）。该酶不能还原一甲基胂酸（MMA(V)）。这种酶的分离和特性表明，在人类中，砷酸盐还原为亚砷酸盐是由酶催化的，而不仅仅是如过去所提出的那样是谷胱甘肽化学还原的结果。
