GSTM5 and age-related macular degeneration: Interestingly, conflicting results on the involvement of GSTM1 and GSTM5 (glutathione s-transferase mu 1/5) polymorphisms and gene expression in AMD pathology exist [51,52], once again suggesting that the necessary balance of the antioxidant system is achieved through the proper activity of several enzymes, and not a single enzyme.