The methods described in this paper are based on h e uricase catalyzed oxidation of uric acid to allantoine and hydrogen p x i d e . By making use of the catalytic activity of peroxidase the generated H f i is measured either spectrophotomedcally with 3 -m e t h y l -b e n z o W b 2 + m hydrazone (MBTH) and 3-dimethylarninobenzoic acid (DMAB) (MI) or fluorimetrically with tylamine (M2) or L-tyrosine (M3). ?he methods are simple, sensitive and selective. The pmcedures developed can be rapidly and readily perf o m d on patient serum samples without deproteinization using 100 pl and 5 pl serum for colorimetric and fluorimetric assay, respectively. Uric acid is a major metabolite of purine substances. Measurements of uric acid levels in biological fluids are of particular significance in the. diagnosis of patients with gout disease. Many colorimetric and fluorimetric methods for the determination of uric acid in biological media have already been published. Diverse enzymatic procedures were surveyed, which are based on the oxidative decomposition of uric acid catalyzed by uricase to hydrogen peroxide. The nascent H202 was detennined by peroxidase catalyzed oxidation of ~h m o g e n i c ~' ~) and fluongenic4') substrates or by catalase mediated conversion of alcohols6') to aldehydes, which were then measured spectrophotometrically.
This paper describes a colorimetric procedure using the << uricase peroxidase MBTWDMAB >> system (MI) and a fluorimedc assay using the << uricase peroxidase tyramine (Mz) or L-tyrosine (M3) system >> for accurate and precise determination of uric acid in serum.