We have developed a fully enzymatic method to measure 1,5 anhydro-D-glucitol (1,5-AG) in serum through use of pyranose oxidase (PROD: EC 1.1.3.10), glucokinase (EC 2.7.1.2), and an ATP-regenerating system. In a previous report (Clin Chem 1989;35:2039-43) the glucose interfering with the measurement of 1,5-AG was removed with a minicolumn. In the method used here, glucokinase and an ATP-regenerating system efficiently convert glucose to the unreactive compound, glucose 6-phosphate, making the method selective for 1,5-AG. The hydrogen peroxide produced in the oxidation of 1,5-AG by PROD is detected with a standard enzymatic color-developing system. The within-run and day-to-day precision (CV) of this method was 0.52-1.29% and 1.17-4.48%, respectively. The correlation (r) between the results obtained with our proposed method (y) and those obtained with the mini-column method (x) was 0.998 (y = 1.007x + 0.493 mg/L; n = 100; Sy/x = 0.641 mg/L). This newly developed method allows quicker and easier measurement of serum 1,5-AG than previously described methods.

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SUMMARY. Renal dipeptidase (EC3.4.l3.l9) activity in serum and urine from healthy volunteers (n = 20), patients with diabetes (n = 18) and patients with chronic renal failure (n = 5) was measured using glycyl-o-alanine as substrate. The assay was highly specific for the enzyme and was not affected by the various aminopeptidases present in serum and urine. No difference in serum renal dipeptidase activity was observed between the groups. The enzyme activity (U/L) in urine was higher than that in serum, irrespective of the group, suggesting the urine concentration was not affected by the serum concentration. The mean renal dipeptidase activities in urine were 2'56,2-46 and 0·78 Urmol creatinine for healthy subjects, patients with diabetes and patients with chronic renal failure, respectively. The renal dipeptidase activity was significantly lower in the chronic renal failure group. The urinary excretion of dipeptidase (Uymmol creatinine) showed significant inverse correlations with that of Ifrmicroglobulin, albumin and IX\-microglobulin, and with serum concentrations of creatinine, Ih-microglobulin and IX\-microglobulin. We suggest that urine dipeptidase may be a useful marker of renal diseases.

Ferritin is an indispensable parameter in the diagnosis of latent iron deficiency anemia or siderosis. In this study, we evaluated the utility of a reagent for ferritin measurement in a latex agglutination (LA) test, using general chemistry analyzers. The intraassay coefficient of variation (CV) was 0.8-3.4% and the interassay CV was 0.0-0.7%. Linearity was observed up to 1100 ng/mL. The effective sensitivity value was 4.0 ng/mL. In addition, good results were obtained with the prozone test, the effects of interferences, correlation with the enzyme immunoassay (EIA) method, and functional assay sensitivity. A significant positive correlation with C-reactive protein (r=0.586, P<0.001) was found. When compared with liver-related biochemical parameters (asparate aminotransferase (AST) and alanine aminotransferase (ALT)) in patients with impaired liver function, ferritin varied in parallel with the liver-related parameters. This assay system was able to measure ferritin accurately over a wide range, and thus could be used to diagnose cancer, siderosis, and iron deficiency anemia. The LA assay system can be employed for measurement with general chemistry analyzers, with rapid and convenient execution. In addition, the LA test allows the simultaneous measurement of other markers of iron deficiency anemia, so clinicians can rapidly obtain examination results.

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