An enzymic assay for ammonia in waste matter

1977 ◽  
Vol 25 (3) ◽  
pp. 688-690 ◽  
Author(s):  
John E. Robbins ◽  
Shane C. Weber
Keyword(s):  
Enzymic Assay

scholarly journals Inhibition of steroid 5α-reductase by specific aliphatic unsaturated fatty acids

1992 ◽  
Vol 285 (2) ◽  
pp. 557-562 ◽  
Author(s):  
T Liang ◽  
S Liao
Keyword(s):  
Fatty Acids ◽  
Oleic Acid ◽  
Linoleic Acid ◽  
Linolenic Acid ◽  
Unsaturated Fatty Acids ◽  
Binding Assay ◽  
Reductase Activity ◽  
Undecylenic Acid ◽  
Gamma Linolenic Acid ◽  
Enzymic Assay

Human or rat microsomal 5 alpha-reductase activity, as measured by enzymic conversion of testosterone into 5 alpha-dihydrotestosterone or by binding of a competitive inhibitor, [3H]17 beta-NN-diethulcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one ([3H]4-MA) to the reductase, is inhibited by low concentrations (less than 10 microM) of certain polyunsaturated fatty acids. The relative inhibitory potencies of unsaturated fatty acids are, in decreasing order: gamma-linolenic acid greater than cis-4,7,10,13,16,19-docosahexaenoic acid = cis-6,9,12,15-octatetraenoic acid = arachidonic acid = alpha-linolenic acid greater than linoleic acid greater than palmitoleic acid greater than oleic acid greater than myristoleic acid. Other unsaturated fatty acids such as undecylenic acid, erucic acid and nervonic acid, are inactive. The methyl esters and alcohol analogues of these compounds, glycerols, phospholipids, saturated fatty acids, retinoids and carotenes were inactive even at 0.2 mM. The results of the binding assay and the enzymic assay correlated well except for elaidic acid and linolelaidic acid, the trans isomers of oleic acid and linoleic acid respectively, which were much less active than their cis isomers in the binding assay but were as potent in the enzymic assay. gamma-Linolenic acid had no effect on the activities of two other rat liver microsomal enzymes: NADH:menadione reductase and glucuronosyl transferase. gamma-Linolenic acid, the most potent inhibitor tested, decreased the Vmax. and increased Km values of substrates, NADPH and testosterone, and promoted dissociation of [3H]4-MA from the microsomal reductase. gamma-Linolenic acid, but not the corresponding saturated fatty acid (stearic acid), inhibited the 5 alpha-reductase activity, but not the 17 beta-dehydrogenase activity, of human prostate cancer cells in culture. These results suggest that unsaturated fatty acids may play an important role in regulating androgen action in target cells.

Evaluation of a modified alcohol dehydrogenase assay for the determination of ethanol in blood.

1982 ◽  
Vol 28 (10) ◽  
pp. 2125-2127 ◽  
Author(s):  
A Poklis ◽  
M A Mackell
Keyword(s):  
Gas Chromatography ◽  
Reaction Time ◽  
Alcohol Dehydrogenase ◽  
Correlation Coefficients ◽  
Least Square ◽  
Standard Curve ◽  
Analytical Recovery ◽  
Sigma Chemical ◽  
Enzymic Assay

Abstract We evaluated a new alcohol dehydrogenase (EC 1.1.1.1) enzymic assay (ADH-glycine, Sigma Chemical Co.) for the determination of ethanol in blood. This assay differs from the manufacturer's previous assay (ADH-pyrophosphate) in that glycine replaces pyrophosphate as the buffer and hydrazine replaces semicarbazide as the trapping agent. The standard curve for the assay was linear over blood ethanol concentrations of 0.50-5.00 g/L. The reaction time of the assay was 10 min. At 1.00 g/L within-run and between-run CVs were 3.96% (n = 20) and 4.01% (n = 20), respectively. Mean analytical recovery of ethanol added to whole blood at 0.50-5.00 g/L was 99.7% (SD 2.6%). We performed 100 consecutive clinical and forensic determinations by the ADH-glycine assay, the ADH-pyrophosphate assay, and gas chromatography. Correlation coefficients of the results by least-square linear regression were 0.995 for ADH-pyrophosphate vs ADH-glycine, and 0.990 for gas chromatography vs ADH-glycine. The major advantage of the ADH-glycine assay over the ADH-pyrophosphate assay is the shorter reaction time, 10 min vs 30 min.

scholarly journals Fatty acyl-CoA esters inhibit glucose-6-phosphatase in rat liver microsomes

1995 ◽  
Vol 307 (2) ◽  
pp. 391-397 ◽  
Author(s):  
R Fulceri ◽  
A Gamberucci ◽  
H M Scott ◽  
R Giunti ◽  
A Burchell ◽  
...  
Keyword(s):  
Palmitic Acid ◽  
Phosphatase Activity ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Fatty Acyl ◽  
Rat Liver Microsomes ◽  
Control Value ◽  
Scattering Measurements ◽  
Induced Changes ◽  
Enzymic Assay

In native rat liver microsomes glucose 6-phosphatase activity is dependent not only on the activity of the glucose-6-phosphatase enzyme (which is lumenal) but also on the transport of glucose-6-phosphate, phosphate and glucose through the respective translocases T1, T2 and T3. By using enzymic assay techniques, palmitoyl-CoA or CoA was found to inhibit glucose-6-phosphatase activity in intact microsomes. The effect of CoA required ATP and fatty acids to form fatty acyl esters. Increasing concentrations (2-50 microM) of CoA (plus ATP and 20 microM added palmitic acid) or of palmitoyl-CoA progressively decreased glucose-6-phosphatase activity to 50% of the control value. The inhibition lowered the Vmax without significantly changing the Km. A non-hydrolysable analogue of palmitoyl-CoA also inhibited, demonstrating that binding of palmitoyl-CoA rather than hydrolysis produces the inhibition. Light-scattering measurements of osmotically induced changes in the size of rat liver microsomal vesicles pre-equilibrated in a low-osmolality buffer demonstrated that palmitoyl-CoA alone or CoA plus ATP and palmitic acid altered the microsomal permeability to glucose 6-phosphate, but not to glucose or phosphate, indicating that T1 is the site of palmitoyl-CoA binding and inhibition of glucose-6-phosphatase activity in native microsomes. The type of inhibition found suggests that liver microsomes may comprise vesicles heterogeneous with respect to glucose-6-phosphate translocase(s), i.e. sensitive or insensitive to fatty acid ester inhibition.

More on enzymic assay of inorganic phosphorus.

1985 ◽  
Vol 31 (7) ◽  
pp. 1242-1242 ◽  
Author(s):  
F Zoppi ◽  
M Giachetti
Keyword(s):  
Inorganic Phosphorus ◽  
Enzymic Assay

One-minute electrochemical enzymic assay for cholesterol in biological materials.

1981 ◽  
Vol 27 (12) ◽  
pp. 1978-1982 ◽  
Author(s):  
L C Clark ◽  
C A Duggan ◽  
T A Grooms ◽  
L M Hart ◽  
M E Moore
Keyword(s):  
Hydrogen Peroxide ◽  
Cholesterol Oxidase ◽  
Density Lipoprotein ◽  
Cholesterol Esters ◽  
Unesterified Cholesterol ◽  
Polycarbonate Membrane ◽  
Platinum Anode ◽  
Tissue Homogenates ◽  
Enzymic Assay ◽  
Kendall Method

Abstract In this rapid and specific micro-scale electrochemical enzymic assay for cholesterol and cholesterol esters, 10 microL of standard or sample is injected directly into a heated (50 degrees C) thermostated, oxystated cuvet containing pH 7.25 buffer, cholesterol oxidase (EC 1.1.3.6), and cholesterol esterase (EC 3.1.1.13). The cholesterol esters are hydrolyzed by the esterase, and the cholesterol is simultaneously oxidized by the oxidase. The hydrogen peroxide produced from oxidation of the unesterified cholesterol is measured by a polarographic anode covered with an acetate/polycarbonate membrane. The membrane allows hydrogen peroxide to diffuse to the platinum anode, where it is oxidized, but prevents the diffusion of ascorbic acid, uric acid, and bilirubin to the electroactive surface. Turbidity does not interfere. The correlation (r) between results by our method and the Abell-Kendall method for 105 samples of serum was 0.9994 and for 105 samples of plasma was 0.9997. Our method is convenient for the analysis of high-density lipoprotein cholesterol in plasma and serum supernates and in many kinds of tissue homogenates. Its limitations are also described.

Sign in / Sign up

Export Citation Format

Share Document