We study the two-dimensional reduction of the Michaelis-Menten reaction of enzyme kinetics. First, we prove the existence and uniqueness of a slow manifold between the horizontal and vertical isoclines. Second, we determine the concavity of all solutions in the first quadrant. Third, we establish the asymptotic behaviour of all solutions near the origin, which generally is not given by a Taylor...

Predator-prey models with Michaelis-Menten-Holling type ratio- dependent functional response exhibit very rich and complex dynamical behavior, such as the existence of degenerate equilibria, appearance of limit cycles and heteroclinic loops, and the coexistence of two attractive equilibria. In this paper, we study heteroclinic bifurcations of such a predator-prey model. We first calculate the h...

The aim of the study was to evaluate level amylase in serum diabetic patients compared healthy controls, glucose, lipids, lipoproteins, thyroid hormones, electrolytes (calcium, potassium, and sodium) transporter enzymes were also studied. (AST), (ALT),(ALP). enzyme purified association between previously mentioned variants it studied other biochemical variables found that there a significant po...

Papain activity in a buffer containing Me2SO was studied using fluorogenic substrates. It was found that the number of active sites of papain decreases with increasing Me2SO concentration whereas the incubation time, in a buffer containing 3% Me2SO does not affect the number of active sites. However, an increase of papain incubation time in the buffer with 3% Me2SO decreased the initial rate of...

Understanding the kinetics of Zn absorption by roots and its effect on morphology this organ is relevant for improving crop management, but still poorly studied common beans. Therefore, an experiment was conducted in a hydroponic system with five initial concentrations (CZnI): 0.0; 1.0; 4.0; 16.0 48.0 µmol L-1. The installed plants at V3 stage development aliquots solution collected over 24 h. ...

Sulfonation is an important metabolic process involved in the excretion and in some cases activation of various endogenous compounds and xenobiotics. This reaction is catalyzed by a family of enzymes named sulfotransferases. The cytosolic human sulfotransferases SULT1A1 and SULT1A3 have overlapping yet distinct substrate specificities. SULT1A1 favors simple phenolic substrates such as p-nitroph...

Michaelis-Menten kinetics are commonly used to represent enzyme-catalysed reactions in biochemical models. The Michaelis-Menten approximation has been thoroughly studied in the context of traditional differential equation models. The presence of small concentrations in biochemical systems, however, encourages the conversion to a discrete stochastic representation. It is shown that the Michaelis...

We determined the Ca(2+) dependence and time course of the modulation of ligand sensitivity in cGMP-gated currents of intact cone photoreceptors. In electro-permeabilized single cones isolated from striped bass, we measured outer segment current amplitude as a function of cGMP or 8Br-cGMP concentrations in the presence of various Ca(2+) levels. The dependence of current amplitude on nucleotide ...

Apo-glucose dehydrogenase existing in Escherichia coli is converted to the holoenzyme with exogenous pyrroloquinoline quinone (PQQ) and Mg(2+). Catalytic behaviour of the E. coli cells with the holoenzyme is characterized by a Michaelis-Menten-type equation with a catalytic constant of the cell and apparent Michaelis constants for D-glucose and an artificial electron acceptor added to the E. co...

The fibrinolytic properties of two molecular forms of extrinsic (tissue-type) plasminogen activator, purified from human melanoma cells in culture, were compared. One form, obtained under protection of aprotinin, consisted of a single polypeptide chain with M, = 72,000 while the other form, obtained without aprotinin, consisted of two polypeptide chains with M, = 30,00040,000 each. The two form...