Reaction intermediate effects on the spectrophotometric uricase assay

The uricase reaction in borate buffer systems has been studied. Gross inaccuracies will be obtained when UV absorbance is monitored at 293 nm unless due regard is given to an absorbing reaction intermediate. The quantitative spectrum of this intermediate was obtained by dynamic difference spectral methods. Interference by this intermediate in the 293 nm assay of uricase may be eliminated using appropriate borate buffer systems. However, borate affects not only the decay rate of the intermediate as previously reported but also the enzyme reaction itself by “salting out” the gaseous substrate, oxygen.