Submitted to: Plant Physiology
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 1995
Publication Date: N/A
Technical Abstract: Oat fructan hydrolase was purified to homogenity as determined by the presence of a single band (43 kD) on a silver-stained SDS-polyacrylamide gel. Oat fructans (avenose) were used to characterize the substrate specificity of the purified enzyme. The purified fructan hydrolase catalyzed hydrolysis of the terminal -2,6 linkage of (6G,6)-kestotetraose 3.5-times more rapidly than it hydrolyzed the terminal -2,6 linkage of 6G-kestotriose and approximately 10 times faster than it hydrolyzed terminal -2,1 linkage of chicory inulin. The Km for avenose ( -2,6 linked fructans with a degree of polymerization of 7 to 14) hydrolysis was 2.8% (w/v) and the Vmax was 0.041 micro mol/min/ml. The Km for hydrolysis of (6G,6)-kestotetraose was 5.6% (w/v) and the Vmax was 0.138 micro mol/min/ml. Catalysis was exolytic and by multiple chain attack. The enzyme had maximal activity at pH 4.5-5.0. Chemical modification of oat fructan hydrolase with n-bromosuccinimide in the presence and absence of avenose identified tryptophan as an essential functional group at or near the active site. Chemical modification with diethylpyrocarbonate suggests that histidine has a significant role in enzyme function but is probably not at the active site.