GSTO1 is a member of the theta class glutathione S-transferase-like (GSTTL) protein family. GSTO1 is expressed in a wide range of human tissues and exhibits glutathione-dependent thiol transferase and dehydroascorbate reductase activities and also catalyzes the reduction of monomethylarsonate, an intermediate in the pathway of arsenic biotransformation. GSTO1 protects from oxidative stress, a risk factor for Alzheimer disease, vascular dementia and stroke. Several polymorphisms in the coding regions of the human GSTO1 have been identified. A polymorphism causing an alanine-to-aspartate (A140D) substitution in amino acid 140 produces a variant with lowered enzyme activities in the arsenic biotransformation. RANDOX recombinant GSTO1 140D comprises a 241 amino acid fragment (1-241) corresponding to the GSTO1 140D mutant mature protein, which is expressed in E. coli with an amino-terminal hexahistidine tag. This product is for research use only and is not intended for diagnostic or therapeutic use.