Figure 3.

Kinetic analysis of XXT1, XXT2, and XXT5. XXT1 and XXT2 assays contained 3 μm XXT and were performed for 30 min; XXT5 assays contained 11.5 μm XXT5 and were performed for 60 min. All reactions contained 50 mm Tris-HCl (pH 7.4), 150 mm NaCl, 1 mm cellohexaose, and 2 mm MnCl₂ and were incubated at 28°C. The kinetic constants K_m and k_cat were calculated by fitting initial velocities as a function of UDP-Xyl concentration using nonlinear curve fitting with Dynafit (Kuzmic, 1996). Products of the enzyme assay were analyzed by HPAEC, quantified by peak integration, and are presented as pmol UDP-Xyl min⁻¹. All enzyme assays were performed in duplicate.