The mixture was filtered through Whatman no.4 filter paper and
incubated at 60oC for 30 hr. The fluorescence intensity was measured by a multimode detector
spectrofluorometer (Model DTX 880, Beckman Coulter, Inc., USA) at an excitation wavelength of
370 nm and an emission wavelength of 440 nm. Aminoguanidine dissolved in 95% ethanol was used as
a standard inhibitor [13].