Purification And Characterization Of A Xanthan-Degrading Enzyme From Microbacterium Sp.XT11

The xanthan-degrading bacterium Microbacterium sp.XT11 could fragment xanthan to form oligosaccharides.However,the molecular mechanism of xanthan degradation by XT11 remains unclear.As one of the xanthan-modification enzymes,xanthan lyase was purified from the fermentation supernatant of the strain XT11 and enzymatic characterization was studied.After the steps of ammonium sulfate precipitation,hydrophbic chromatography,Q-Sephadex chromatography and DEAE-cellulose chromatography,a xanthan lyase with a molecular mass of 110 kDa and a specific activity of 69.6 U/mg was purified.The enzyme is specific for intact xantan with pyruvated mannosyl side chain and optimally active at pH 6.0?6.5 and 40 ?.K+,Ca2+,Na+,Mg2+,Mn2+,Li+ significantly enhanced the activity of the enzyme.The activity of the xanthan lyase was intensely inhibited by Zn2+,whereas Cu2+ almost completely inhibited the enzymatic reaction.The purified enzyme exhibited a typical Michaelis-Menten kinetics,the Km and Vmax values for xanthan were 4.23 mg/mL and 8.22 ?moL/(min·L),respectively.This work should be valuable for clarifying the cleaving mechanism of xanthan lyase and preparing modified xanthan with novel rheological properties.