Alanine and glutamine transport have been studied during red blood cell maturation in the rat. Kinetic parameters of Na(+)-dependent L-alanine transport were: Km 0.43 and 1.88 mM and Vmax 158 and 45 nmoles/ml ICW/min for reticulocytes and erythrocytes, respectively. During red cell maturation in the rat there is a loss of capacity and affinity of the system ASC for L-alanine transport. The valu...

By coupling mitochondrial ATP production to an enzymatic NADPH-producing reaction, we monitored the rates of ATP production spectrophotometrically. ATP production was coupled to the oxidation of malate and pyruvate. Interference by adenylate kinase was eliminated by using P1,P5-di(adenosine-59)pentaphosphate and we found no interference by NADPH oxidase. We studied the kinetics of ATP synthesis...

Erythromonas ursincola, strain KR99 isolated from a freshwater thermal spring of Kamchatka Island in Russia, resists and reduces very high levels of toxic tellurite under aerobic conditions. Reduction is carried out by a constitutively expressed membrane associated enzyme, which was purified and characterized. The tellurite reductase has a molecular weight of 117 kDa, and is comprised of two su...

Variability in activity of CYP2C9, which is involved in the metabolism of approximately 15% of current therapeutic drugs, is an important contributor to interindividual differences in drug response. To evaluate the functional alternations of CYP2C9(*)2, CYP2C9(*)3, CYP2C9(*)8, CYP2C9(*)11 and CYP2C9(*)31, identified in our previous study in Chinese Han population, allelic variants as well as th...

The effects of various metal ions (Na, K, Ca, Mg, Al, Co) and anions (Cl, and CH3COO) on two cellulases were investigated. Fitting of the data to Michaelis-Menten kinetics showed that Al noncompetitively inhibited cellulase (Km = 22.68 g/L; Vmax = 0.269 mg/min at 5.0 mmol/L AlCl3) and Mg competitively inhibited cellulase (Km = 50.0 g/L; Vmax = 0.434 mg/min at 10.0 mmol/L MgCl2) Different metal ...

The effect of hypothermia on the in vivo pharmacokinetics of midazolam was evaluated, with a focus on altered metabolism in the liver and binding to serum proteins. Rat primary hepatocytes were incubated with midazolam (which is metabolized mainly by CYP3A2) at 37, 32 or 28 °C. The Michaelis-Menten constant (Km) and maximum velocity (Vmax) of midazolam were estimated using the Michaelis-Menten ...

The major inducible trimethylamine oxide reductase was purified from Salmonella typhimurium LT2. The molecular weights of the native enzyme were estimated to be 332,000 by gel filtration and 170,000 by nondenaturing disc gel electrophoresis. In sodium dodecyl sulfate-gel electrophoresis, the enzyme formed a single band of molecular weight 84,000. The isoelectric point was 4.28. Maximum activity...

Alcaligenes sp. MTCC 10674 has a bienzymatic system for the hydrolysis of nitriles. The nitrile hydratase and amidase have been purified simultaneously to homogeneity using a combination of (NH)4SO4 precipitation, ion exchange chromatography and gel permeation chromatography. Nitrile hydratase and amidase have molecular weight of 47 and 114 kDa, respectively and exist as heterodimer. Optimum te...

Spergualin (SG) and 15-deoxyspergualin (DSG) are derivatives of spermidine. Their substrate and inhibitor activities toward amine oxidase from bovine plasma were determined. SG was a good substrate of amine oxidase next to spermidine. The Km and Vmax for SG were 46.5 microM and 0.429 microM/minute, respectively, whereas the Km and Vmax for spermidine were 111 microM and 3.75 microM/minute, resp...

An algorithm for the least-squares estimation of enzyme parameters Km and Vmax. is proposed and its performance analysed. The problem is non-linear, but the algorithm is algebraic and does not require initial parameter estimates. On a spreadsheet program such as MINITAB, it may be coded in as few as ten instructions. The algorithm derives an intermediate estimate of Km and Vmax. appropriate to ...