x1 = M
x2 = MpY
x3 = MpT
x4 = Mpp
x5 = MAPKK
x6 = MKP
x7 = MpY_MAPKK
x8 = MpT_MAPKK
x9 = M_MAPKK_Y
x10 = M_MAPKK_T
x11 = Mpp_MKP_Y
x12 = Mpp_MKP_T
x13 = MpY_MKP_Y
x14 = MpY_MKP_T
x15 = MpT_MKP_Y
x16 = MpT_MKP_T
x17 = M_MKP_T
x18 = M_MKP_Y