FIG. 2.

Effect of the molar ratio of borate to fructose on the conversion of fructose to psicose by A. tumefaciens d-psicose 3-epimerase. The reactions were performed at pH 9.0 and 50°C for 3 h using 100 mM fructose and 0 to 100 mM borate. The conversion yields of psicose from fructose obtained from experimental data (•) are the means of results from three experiments. The theoretical conversion yields of psicose (○) were calculated based on the amount of available fructose, excluding the initially formed fructose-borate complex, and are the means of results from 20 experiments. The line indicates the theoretical maximum level of conversion of fructose to psicose with the addition of borate.