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.