title: An enzymatic assay of inorganic phosphate in serum using nucleoside phosphorylase and xanthine oxidase.
abstract: We have developed a new enzymatic assay for the determination of inorganic phosphate (Pi) in serum, using nucleoside phosphorylase (NP) and xanthine oxidase (XOD). Pi and inosine react to form hypoxanthine and ribose-1-phosphate. The hypoxanthine is oxidized to xanthine, which is further oxidized to uric acid. In these two reactions 2,6-dichlorophenol-indophenol (DCIP) is reduced to a colourless compound and the decrease in colour is measured spectrophotometrically at 600 nm. The assay is automated with an RA-XT analyser. The precision of the automated assay is acceptable (C.V. < 3.5%) and results are accurate and linear across a range of values from 0.2-2.5 mmol/l. The assay correlates well with molybdate methods carried out on SMAC III and RA-XT analysers (r values 0.99 and 0.98, respectively), and seems to be less prone to non-specific sample interference than the usual RA-XT method. The enzymatic assay described seems to be suitable for the routine determination of serum Pi.
authors.affiliation: Department of Chemical Pathology, Medical Faculty, University of Pretoria, South Africa.
authors.forename: J P
authors.initials: JP
authors.lastname: Ungerer
authors.forename: H M
authors.initials: HM
authors.lastname: Oosthuizen
authors.forename: S H
authors.initials: SH
authors.lastname: Bissbort
mesh_terms: D006801:Humans; D010084:Oxidation-Reduction; D010430:Pentosyltransferases; D010710:Phosphates / Q000097:blood*; D013053:Spectrophotometry; D014969:Xanthine Oxidase
chemical_list: D010710:Phosphates; D014969:Xanthine Oxidase; D010430:Pentosyltransferases; C067995:nucleoside phosphorylase