A rapid and accurate method is described for the assay of cholesterol ester hydrolase (CEH) activity. Aliquots of the enzyme-substrate incubation mixture are extracted into isopropanol. The free cholesterol concentration in each extract is determined enzymatically using a single aqueous reagent containing cholesterol oxidase and peroxidase. The free cholesterol remaining after the cholesterol e...

This work describes a droplet microarray for monitoring of enzymatic activity on a glass surface. These array are composed of features defined and separated by differential surface tension (surface tension array). A photolithographic method was used to create a series of circular hydrophilic spots delimited by a perfluorosilanated surface. The perfluorinated region had water contact angle on th...

We describe a new and improved enzymatic assay for determining the concentration of D-mannose in sera. Serum D-glucose is selectively converted to glucose-6 phosphate with the highly specific thermostable glucokinase (EC 2.7.1.2) from Bacillus stearothermophilus. The anionic reaction products and excess substrates are removed by a rapid and simple anion-exchange chromatography step in microcent...

References 1. Linder MW, Prough RA, Valdes R. Pharmacogenetics: a laboratory tool for optimizing therapeutic efficacy. Clin Chem 1997;43:254–66. 2. Raimundo S, Fischer J, Eichelbaum M, Griese EU, Schwab M, Zanger UM. Elucidation of the genetic basis of the common ‘intermediate metabolizer’ phenotype for drug oxidation by CYP2D6. Pharmacogenetics 2000;10:577– 81. 3. Sachse C, Brockmoller J, Baue...

Vol.33, No.2, 1987 in June 1986, after recahibration of the glucose method, gave results equal to the survey mean: 640 and 1110 mg/L, respectively. The addition of two more calibration points solved our problem. However, we do not want to imply that five or more calibration points are required. The important question is not how many calibration points are used, but rather, are the concentration...

We describe an improved enzymatic method for assaying magnesium in serum, plasma, or urine. Magnesium participates as an Mg.ATP complex in a reaction catalyzed by glucokinase (EC 2.7.1.2) coupled to an NADP+-dependent glucose-6-phosphate dehydrogenase (EC 1.1.1.49) reaction. The increase of absorbance at 340 nm, due to the NADPH produced, is proportional to the amount of the activated glucokina...

A method is described for the assay of gentamicin using the enzyme gentamicin adenylyltransferase derived from an R-factor-carrying strain of Escherichia coli. The reaction involves adenylylation of the gentamicin with ((14)C)-ATP to form a radioactively labelled product. The technique is compared with the plate diffusion and the urease methods. The adenylylation technique gives results compara...

A new enzymatic method for assaying iron in serum samples, suitable for automated analyzers, is reported. Three reagent mixtures are used: dilution buffer (pH 3.0; ascorbate), reagent 1 (pH 6.7; apoaconitase), and reagent 2 (pH 7.7; citrate, magnesium, and isocitrate dehydrogenase). Sera are diluted with dilution buffer. Fe3+ is liberated from transferrin in sera under acidic conditions, and th...

HYPOTHESIS An enzymatic assay for quantification of γ-hydroxybutyric acid (GHB) in biofluids can be employed for targeted screening of succinic semialdehyde dehydrogenase deficiency (SSADHD) in selected populations. RATIONALE We used a two-tiered study approach, in which the first study (proof of concept) examined 7 urine samples derived from patients with SSADHD and 5 controls, and the secon...