This studydescribesamodifiedcolorimetricassay foruricase activity in flexible 96-well microtiter plates using the uricase/ uric acid/horseradish peroxidase/4-aminoantipyrine/3,5-dichloro-2-hydroxybenzene sulfonate colorimetric reaction. The utility of this assay was demonstrated in a screen for mutant uricase enzymes derived from theuricasegene of the thermophilic bacteriumBacillus subtilisby a modified stag-gered extension process (StEP) mutagenesis. AnEscherichia coli library of StEP-derived uricase mutant clones was screened yielding two identical active mutanturicasegenes
