The metabolism of a number of compounds by the cytochrome P-450 subfamily CYP3A does not exhibit classic Michaelis-Menten kinetics but displays a sigmoidal rate-substrate concentration relationship. Intrinsic clearance (CLint) cannot be calculated for these drugs due to the lack of a first order region in their kinetic profiles, and a suitable parameter has yet to be identified to allow such da...

We study chemical reactions with complex mechanisms under two assumptions: (i) intermediates are present in small amounts (this is the quasi-steady-state hypothesis or QSS) and (ii) they are in equilibrium relations with substrates (this is the quasiequilibrium hypothesis or QE). Under these assumptions, we prove the generalized mass action law together with the basic relations between kinetic ...

Glutamate dehydrogenase, GDH (L-glutamate:NAD+ oxidoreductase (deaminating) EC 1.4.1.2) was purified from the plant fraction of lupin nodules and the purity of the preparation established by gel electrophoresis and electrofocusing. The purified enzyme existed as 4 charge isozymes with a MW of 270000. The subunit MW, as determined by dodecyl sulphate electrophoresis, was 45000. On the basis of t...

In batch cultures of four Mediterranean strains (from France, Italy, and Spain) of Alexandrium catenella (Whedon et Kof.) Balech growing on a daily light cycle, ammonium and urea uptake were estimated by the (15) N tracer technique. Ammonium uptake could be described by Michaelis-Menten kinetics along a substrate gradient of 0.1-10 μgat N · L(-1) for the four strains, while two different patter...

The rate of hydrochloric acid production by isolated, bullfrog gastric mucosae depends critically on the supply of chloride ion to the serosal surface. Secretion of acid is negligible if chloride is completely replaced by glucuronate and gluconate ion. The experimental evidence indicates that the rate of acid secretion may be regarded as a reaction velocity, depending on chloride concentration ...

The equation commonly called the Michaelis-Menten equation is sometimes attributed to other authors. However, although Victor Henri had derived the equation from the correct mechanism, and Adrian Brown before him had proposed the idea of enzyme saturation, it was Leonor Michaelis and Maud Menten who showed that this mechanism could also be deduced on the basis of an experimental approach that p...

Dynamic co-operativity in monomeric enzymes is characterized in terms of a non-Michaelis-Menten kinetic behaviour. The latter is believed to be associated with mechanisms that include multiple reaction pathways due to enzymatic conformational fluctuations. Recent advances in single-molecule fluorescence spectroscopy have provided new fundamental insights on the possible mechanisms underlying re...

Rhus chinensis Mill is a potential plant for phytoremediation of Pb and able to uptake copious amount Pb. However, little known about the pathways properties in this plant. Here, controlled experiments were used assess translocation R. chinensis. The whole time-kinetics divided into two stages: rapid slower accumulation, processes fitted with linear model. concentration-dependent kinetics chara...