5.1.99.7	native enzyme 954fold by ammonium sulfate fractionation, Cibacron blue 3GA affinity chromatography, hydrophobic interaction chromatography, methotrexate affinity chromatography, and ge filtration, to homogeneity	
5.1.99.7	recombinant enzyme	
5.1.99.7	recombinant enzyme 2.7fold from Escherichia coli strain M15 by anion exchange chromatography, ultrafiltration, heat treatment at 80°C for 4 min, and gel filtration