GSTP1 and asthma: Most studies investigating genetically associated susceptibility to respiratory abnormalities have focused on GSPT1, the most abundant GST isozyme in the lungs, as well as GSTM1 and GSTT1. The functional sequence variant in GSTP1 at codon 105 (Ile105Val -rs1695) has been associated with asthma in some [20, 21] but not all studies [22].