원문정보
초록
영어
The conversion from D-fructose to D-psicose by Agrobacterium tumefaciens D-psicose 3-epimerase was carried out with borate. The activity for maximum D-psicose production with borate was higher than that without borate and it was shifted toward alkaline condition of pH 9.0. The chemical structures, association constants (KA), and inhibitor constants (KI) of the sugars showed that the complex of borate with d-psicose was formed as larger content than that with D-fructose. The binding ratio between sugar and borate (or boric acid) in the complex was determined to be 1:1 by an electrospray ionizationmass spectrometry. When the borate ratio to sugar was increased, the reverse reaction from D-psicose to D-fructose by the enzyme was inhibited while the forward reaction from D-fructose to D-psicose was stimulated within 60% (mol/mol) borate ratio to d-fructose. Above 60% borate ratio, the conversion decreased due to the decrease of borate binding to D-psicose. Using 60% borate ratio, D-psicose of 440 g/l was produced from 700 g/l D-fructose, corresponding to 63% conversion yield. The conversion yield
was higher than the equilibrium (33%) of the enzyme.