title: Assay of magnesium in serum and urine with use of only one enzyme, isocitrate dehydrogenase (NADP+).
abstract: We report a method for assaying magnesium in serum and urine involving only one enzyme, isocitrate dehydrogenase (NADP+)(EC 1.1.1.42), which requires magnesium ion for activity. The enzymatic reduction of NADP+ by isocitrate increases in rate linearly up to at least 20 mmol/L magnesium in the presence of appropriate concentrations of the two metal-chelating reagents, EDTA and glycol ether diamine-N,N,N',N'-tetraacetate. Within-run (n = 20) CVs and day-to-day (n = 10) CVs for sera are < or = 1.5% and < or = 2.6%, respectively. Analytical recovery of magnesium in sera averages 96-100%. This method is not affected by bilirubin, hemoglobin, or lipemia. The method (y) gives the following results correlating with atomic absorption spectrophotometry (x): y = 1.03x + 0.06 mmol/L (n = 62, r = 0.995, Sylx = 0.03) for sera, and y = 1.03x - 0.10 mmol/L (n = 62, r = 0.989, Sylx = 0.19) for urines; with the calmagite method (x): y = 0.99x + 0.04 mmol/L (n = 62, r = 0.991, Sylx = 0.03) for sera, and y = 0.98x + 0.03 mmol/L (n = 62, r = 0.999, Sylx = 0.02) for urines.
authors.affiliation: Biochemical Research and Development Center, Oriental Yeast Co., Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Fujita
authors.forename: Y
authors.initials: Y
authors.lastname: Kawakami
authors.forename: S
authors.initials: S
authors.lastname: Kohda
authors.forename: S
authors.initials: S
authors.lastname: Takata
authors.forename: Y
authors.initials: Y
authors.lastname: Sunahara
authors.forename: K
authors.initials: K
authors.lastname: Arisue
mesh_terms: D001322:Autoanalysis / Q000706:statistics & numerical data; D001391:Azo Compounds; D002122:Calcium Chloride / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007521:Isocitrate Dehydrogenase / Q000378:metabolism*; D007523:Isocitrates / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000097:blood* / Q000652:urine*; D009249:NADP / Q000494:pharmacology*; D010084:Oxidation-Reduction; D011786:Quality Control; D012680:Sensitivity and Specificity
chemical_list: D001391:Azo Compounds; D007523:Isocitrates; C006876:calmagite; D004533:Egtazic Acid; D009249:NADP; D004492:Edetic Acid; C034219:isocitric acid; D007521:Isocitrate Dehydrogenase; D008274:Magnesium; D002122:Calcium Chloride