Michaelis-Menten behavior

Mathematically, the Michaelis-Menten equation is the equation of a rectangular hyperbola. Sometimes you ll here reference to hyperbolic kinetics, this means it follows the Michaelis-Menten equation. A number of other names also imply that a particular enzyme obeys the Michaelis-Menten equation Michaelis-Menten behavior, saturation kinetics, and hyperbolic kinetics. 

Zn2+-catalyzed cleavage of (Zn2+ HPNPP)2 in ethanol discussed above.85 For the slower reacting MNPP, the chemical cleavage step (represented by k3 and requiring a methoxide which is probably coordinated to one or both of the metal ions in 35 2Zn(II)) is relatively slow, so that both the pre-equilibrium steps are established and typical Michaelis-Menten behavior is observed with saturation at higher [35 2Zn(II)]. On the other hand, with the far more reactive HPNPP the chemical cyclization step, /c3, is proposed to be faster than the k 2 step in the concentration range of 35 2Zn(II) used here. In this event, the observed kinetics would be linear in [35 2Zn(II)] as is the case in Fig. 20, with kohs — /c, [35 2Zn(I )]k2/(k, + k2). 

Carrier-mediated passage of a molecular entity across a membrane (or other barrier). Facilitated transport follows saturation kinetics ie, the rate of transport at elevated concentrations of the transportable substrate reaches a maximum that reflects the concentration of carriers/transporters. In this respect, the kinetics resemble the Michaelis-Menten behavior of enzyme-catalyzed reactions. Facilitated diffusion systems are often stereo-specific, and they are subject to competitive inhibition. Facilitated transport systems are also distinguished from active transport systems which work against a concentration barrier and require a source of free energy. Simple diffusion often occurs in parallel to facilitated diffusion, and one must correct facilitated transport for the basal rate. This is usually evident when a plot of transport rate versus substrate concentration reaches a limiting nonzero rate at saturating substrate While the term passive transport has been used synonymously with facilitated transport, others have suggested that this term may be confused with or mistaken for simple diffusion. See Membrane Transport Kinetics... 

Non Michaelis-Menten behavior (i.e., no saturation kinetics in presence of excess HC03) was observed and the second-order rate constants for the catalyzed decarboxylation (/ = k k<>j(k i / 2) for... 

The Kinetic Properties of Allosteric Enzymes Diverge from Michaelis-Menten Behavior... 

Corey also pointed out that 16 reflects the transition-state of an enzyme-substrate complex. Its formation was later supported by the observation of Michaelis-Menten-type kinetics in dihydroxylation reactions and in competitive inhibition studies [37], This kinetic behavior was held responsible for the non-linearity in the Eyring diagrams, which would otherwise be inconsistent with a concerted mechanism. Contrary, Sharpless stated that the observed Michaelis-Menten behavior in the catalytic AD would result from a step other than osmylation. Kinetic studies on the stoichiometric AD of styrene under conditions that replicate the organic phase of the catalytic AD had revealed that the rate expression was clearly first-order in substrate over a wide range of concentrations [38],... 

To study the effect of polymer size on catalysis [37], pyridoxamine was linked to a series of PEIs with Mn = 600,1800,10 000, and 60 000, both simply permethylated and with additional attached dodecyl chains. The polymers were examined in the transamination of pyruvic acid and of phenylpyruvic acid, showing Michaelis-Menten behavior. The k2 and of i M determined showed only small variations with polymer size. Thus, the strong advantage of pyridoxamines attached to the Mn = 60 000 PEI, relative to simple pyridoxamine alone, was seen to almost the same extent with the smaller... 

Figure 13.3a shows a plot of the rate of packaging as a function of the ATP concentration under a constant force of 5pN. This data is well described by the characteristic Michaelis-Menten behavior with a Pmax 100 bp s and a Km 30 gM. Interestingly, the fit, done to a Michaelis-Menten-Hill equation reveals a Hill coefficient n I, indicating that the binding of the ATP to the motor is not cooperative. These same studies revealed that ADP is a competitive inhibitor of the motor and that phosphate release should be a nearly irreversible step [55], as its concentration in solution can be varied three orders of magnitude without affecting the rate of the motor. 

An enzyme converts substrate S to product P, and obeys simple one-substrate Michaelis-Menten behavior. The following rate data were obtained with a 5 x 10-8M enzyme at 25 °C in a pH 7.2 phosphate buffer ... 

Particularly interesting is the fact-evidenced in Figure 7A that the kinetics operated by the liposomes follows a Michaelis-Menten behavior. The corresponding turnover is illustrated in Figure 7B to what an extent a turnover is really present in these experiments is however not ascertained yet. 

Autoregulatory action helps to reduce nerve cell destruction resulting from brain tissue anoxia. Two possible mechanisms include flow controller dynamics in the form of pure delays and time constant lags and oxygen consumption control with Michaelis-Menten behavior. Response curves also suggest the possibility of facilitated or active transport of oxygen in tissue and resistance to the diffusion of oxygen from the tissue into the blood stream. 

All catalytic systems studied display Michaelis-Menten behavior. Compared to the protein-free catalyst (Table 3, entry 1) all artificial hydrogenases display higher affinity for the substrate (i.e., smaller K, entries 2-4) and increased turnover frequencies (i.e., larger k ). It thus appears that incorporation of a biotinylated catalyst within streptavidin contributes to improve both its selectivity and its activity. We hypothesize that this latter feature may be caused by the accumulation of the hydrophobic substrate and in the vicinity of the active site, which bears hydrophobic amino acid residues. 

An interesting feature of this reaction system is that the rate-concentration profile showed the Michaelis-Menten behavior, as shown in Figure 12. In Table II are tabulated the kinetic quantities defined in Equation (6), which reads... 

Figure 1. Idealized (A) velocity vs. substrate concentration and (B) double reciprocal plots (Lineweaver-Burk) for enzymes demonstrating (a) hyperbolic (classical Michaelis-Menten) behavior (b) positive cooperativity (c) negative cooperativity.

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