GSTM1 and Parkinson disease: On the other hand, there are synergistic effects on PD in polymorphisms of CYPs and GSTs, that is, the protection conferred, respectively, by simultaneous presence of the rs12441817/CC (CYP1A1) and rs2070676/GG + GC (CYP2E1) genotypes, as well as of the GSTM1-present, GSTT1-null, rs156697/AG + GG (GSTO2) and rs1695/AA (GSTP1) genotypes.