Table 3.

Kinetic parameters of WT, L356Q, and I139V of AgApiT

Substrate	Enzyme	K m (µM)	k cat (×10−3 s−1)	k cat/Km (M−1 s−1)
UDP-apiose	WT	8.6 ± 0.6	0.65 ± 0.01	76 ± 6
	I139V	17 ± 1	0.47 ± 0.01	28 ± 3
	L356Q	390 ± 60	0.14 ± 0.01	0.36 ± 0.08
Apigenin 7-O-glucoside	WT	15 ± 3	0.88 ± 0.05	58 ± 15
	I139V	17 ± 1	0.83 ± 0.07	50 ± 18
	L356Q	52 ± 9	0.21 ± 0.02	2.1 ± 0.3

These means and Sd were calculated from the nonlinear curves obtained from 3 measurements at each concentration of individual substrates.