Continuous spectrophotometric assay for β-glucuronidase

A continuous spectrophotometric assay has been developed for detecting beta -glucuronidase activity. In the assay, Para-nitrophenyl beta -D-glucuronide is cleaved to yield a chromophoric product. With the commercial E. coli enzyme, it is demonstrated that the reactions can be continuously monitored by the increase of absorbance at 405 nm. The method is highly sensitive and able to detect less than 1.4 x 10(-4) U/mL of the enzyme activity in solution. Such a new assay offers significant advantages over the existing discontinuous methods and should be useful for both routine enzyme assay and accurate kinetic studies.