Table 1
3.4 Determination of At ATAs’ kinetic parameters under different DMSO concentrations
To investigate the catalytic efficiency of T23I/T200K/P260S, the kinetic parameters were assayed by using 1-acetylnaphthalene (amino acceptor) and 1-(R )-PEA (amino donor) as substrates. Under 25%, 35% and 45% DMSO, M3 displayed higher k cat values than WT toward 1-acetylnaphthalene. And the K m values of M3 for 1-acetylnaphthalene decreased compared with WT under different concentrations of DMSO (13.44, 14.70, and 30.27 mM vs 15.84, 22.01, and 43.62 mM, Table 2). The catalytic efficiency (k cat/K m) between WT and M3 had little difference. As for 1-(R )-PEA, the two enzymes of WT and M3 showed similar k cat values. However, theK m values of M3 decreased significantly. Thek cat/K m values of M3 increased 7.25-, 5.66-, and 3.67-fold higher than WT under 25%, 35%, and 45% DMSO toward 1-(R )-PEA. With the DMSO concentration increasing, the catalytic efficiency of WT and M3 gradually reduced, which indicated that the high concentration of DMSO could inhibit the catalytic efficiency or destroy the optimal conformation of At ATA toward 1-acetylnaphthalene and 1-(R )-PEA.