By combining the Michaelis-Menten kinetics of metabolism with the two-stage model of Moolgavkar and Knudson (1981) and the extended two-stage model of carcinogenesis proposed by Tan and Gastardo (1985), this paper proceeds to investigate the effects of metabolism of carcinogens on cancer tumor development. It is shown that the nonlinear kinetics of metabolism of carcinogens affect the dose-resp...

Abstract. Ectoenzymatic activity, prokaryotic heterotrophic abundances and production were determined in the Mediterranean Sea. Sampling was carried out sub-surface, deep chlorophyll maximum layer (DCM), core of Levantine intermediate waters deeper part mesopelagic layers. Michaelis–Menten kinetics assessed using a large range concentrations fluorogenic substrates (0.025 to 50 µM). As consequen...

Inulosucrases catalyze transfer of a fructose moiety from sucrose to a water molecule (hydrolysis) or to an acceptor molecule (transferase), yielding inulin. Bacterial inulin production is rare and a biochemical analysis of inulosucrase enzymes has not been reported. Here we report biochemical characteristics of a purified recombinant inulosucrase enzyme from Lactobacillus reuteri. It displayed...

Soybean lipoxygenase-1 kinetics are known to show product and substrate inhibition. With linoleic acid as the substrate and using a simple Michaelis-Menten formulation, we have shown that K(ss), the substrate inhibition constant was increased by more than five-fold when initial oxygen concentration was increased from 228 to 1140 microM. Excess substrate inhibition is in fact almost avoided at h...

The unidirectional influx of cycloleucine into in vitro preparations of gill tissue of the mussel, Mytilus californianus, was determined. Influx was found to be linear for at least an hour, and the kinetics of cycloleucine influx conformed to Michaelis-Menten type kinetics. The transport mechanism(s) for cycloleucine is relatively specific for the L-enantiomorph of neutral amino acids, and is c...

Two forms of glutathione S-aryltransferase were purified from rat liver. The only differences noted between the two forms were in the chromatographic and electrophoretic properties, which permitted the separation of the two species. The molecular weights of the enzyme and its subunits were estimated as about 50000 and 23000 respectively. The steady-state kinetics did no follow Michaelis-Menten ...

The cytochrome P450s (CYPs) are the major enzymatic detoxification and drug metabolism system. Recently, it has become clear that several CYP isoforms exhibit positive and negative homotropic cooperativity. However, the toxicological implications of allosteric kinetics have not been considered, nor understood. The allosteric kinetics are particularly enigmatic in several respects. In many cases...

Quantitative biology relies on the construction of accurate mathematical models, yet the e↵ectiveness of these models is often predicated on making simplifying approximations that allow for direct comparisons with available experimental data. The Michaelis-Menten approximation is widely used in both deterministic and discrete stochastic models of intracellular reaction networks, due to the ubiq...

Methods to treat kinetic data for the biodegradation of different plastic materials are comparatively discussed. Different samples commercial formulates were tested aerobic in compost, following standard ISO14855. Starting from raw data, conversion vs. time entries elaborated using relatively simple models, such as integrated equations zero, first and second order, through Wilkinson model, or a...