Study on the enzymatic properties of Uridine Diphosphate Glucose:phloretin-2'-O-glycosyltransferase from Malus x Domestica

Uridine Diphosphate Glucose: phloretin-2'-O-glycosyltransferase from Malus x Domestica( Md P2'GT)was purified using the ammonium sulfate precipitation,DEAE-Sepharose anion-exchange and Sephadex G75 gel filtration chromatography procedures to apparent homogeneity.Specific activity for purified enzyme was 632.0 U / mg.The purfication fold was 71.0 and recovery rate was 42.6%.The molecular weight was estimated to be 50 ku by SDS-PAGE.The purified enzyme catalyzed the glycosylation reaction with optimal activity at p H8.5 and was stable over a range of p H7.0 ~ 9.0. The optimal temperature for enzyme activity was 45 ℃. The Kmvalue for Md P2 'GT was determined to be 3.16 μmol / L,and Vmaxwas 0.77 n M / min·mg protein. At the concentration of 5 mmol / L,Md P2'GT was found to be activated by the presence of Ca2 +and Mg2 +ions. The activity of Md P2 'GT was not apparently affected by Na+or K+,but it was significantly inhibited by Al3 +,Cu2 +,Mn2 +and Zn2 +.The inhibition effect of Cu2 +was the strongest( p < 0.05).Md P2'GT exhibits p H stability under alkaline condition and thermal stability,which has potential applications in the respect of enzymatic synthesis of phloridzin.