Copper amine oxidases (CAOs) catalyse the oxidative de-amination of biogenic amines which are ubiquitous compounds essential for cell growth and proliferation. The enzymes are homodimers containing both topaquinone and a Cu(II) ions as cofactors at the active site of each subunit. After extraction and purification of chickpea (cicer arietinum) amine oxidase by chromatoghraphy, Km and Vmax of th...

Nicotinamide-(S-methylmercury-thioinosine) dinucleotide was formed by reaction of nicotinamide-(6-thiopurine) dinucleotide with methylmercury chloride. The compound exhibits coenzyme properties in the test with LDH (Km=1.5 X 10(-4) M, Vmax=12500) and LADH (Km=1.7 X 10(-4) M, Vmax=27) and inactivates YADH and GAPDH. From incubations with LDH and LADH the mercury containing coenzyme could be reg...

The effect of Tris, Glycine and Tricine on alkaline phosphatase activity was tested at a pH of 8.6, 8.85 and 9.1, using pNPP as substrate. Alkaline phosphatase activity was measured by monitoring the increase in NP absorbance at 420nm using a spectrophotometer. Alkaline phosphatase in Tris buffer at pH 9.1 was found to have the highest activity. MichaelisMenten enzyme kinetic analysis revealed ...

The mechanism and substrate specificity of the phosphotriesterase from Pseudomonas diminuta have been examined. The enzyme hydrolyzes a large number of phosphotriester substrates in addition to paraoxon (diethyl p-nitrophenyl phosphate) and its thiophosphate analogue, parathion. The two ethyl groups in paraoxon can be changed to propyl and butyl groups, but the maximal velocity and Km values de...

The glutamate transport system of the bovine renal epithelial cell line NBL-1 was studied. The Km for Na+-dependent glutamate transport was found to be 13.8 + 2.4 ,ltM (Vmax. 365 + 19.2 pmol/3 min per mg) and for Na+-dependent aspartate transport 4.5 + 1.1 ,uM (Vmax. 108 6.3 pmol/3 min per mg). The Km values are in close agreement with those expected for high-affinity Na+-dependent glutamate tr...

In a genetically engineered V79 cell line (XEMd-MZ) expressing rat cytochrome P4501A2 the activity of phenacetin-O-deethylase was determined and compared with freshly isolated rat hepatocytes. In the V79 cells the apparent Km was 0.99 microM (N = 4), compared to the high affinity Km (0.23 microM, N = 4) found in freshly isolated rat hepatocytes, where as the Vmax found in the XEMd-MZ cells (14....

Folylpolyglutamyl synthetase (FPGS), partially purified from murine L1210 leukemia and Sarcoma 180 cells and the proliferative fraction of luminal epithelium from mouse small intestine (the site of limiting toxicity to folate analogues), was examined for its ability to utilize various 4-aminofolates as substrates. For tumor-derived FPGS, aminopterin was the most preferred substrate overall, exh...

The kinetic properties of enzymes are often reported using the apparent KM and Vmax appropriate to the standard Michaelis-Menten enzyme. However, this model is inappropriate to enzymes that have more than one substrate or where the rate expression does not apply for other reasons. Consequently, it is desirable to have a means of estimating the appropriate kinetic parameters from the apparent va...

Crude wild pear lipoxygenase (LOX) from ripe Kurdistan wild pears was used in this study. Extracted crude LOX was assayed spectrophotometrically for raw, ripe wild pear lipoxygenase and after 7-day storage. The effects of different buffers and pHs, substrate preparations, temperature, inhibitors and metal ions on LOX activity were evaluated at three conditions. The enzyme was most active with H...

While the metabolic activation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) by N-hydroxylation has been well documented, the relative roles of the human cytochrome P450 (CYP) enzymes that catalyze this reaction have not been established. Previous studies indicated that the mutagenic activation product, 2-hydroxyamino-PhIP (N2-OH-PhIP), is produced primarily by CYP1A2, and to a less...