Lineweaver-Burk plot. See

In addition to the Lineweaver-Burk plot (see p.92), the Eadie-Hofstee plot is also commonly used. In this case, the velocity v is plotted against v /[A]. In this type of plot, Vmax corresponds to the intersection of the approximation lines with the v axis, while Km is derived from the gradient of the lines. Competitive and non-competitive inhibitors are also easily distinguishable in the Eadie-Hofstee plot. As mentioned earlier, competitive inhibitors only influence Km, and not Vmax- The lines obtained in the absence and presence of an inhibitor therefore intersect on the ordinate. Non-competitive inhibitors produce lines that have the same slope (llower level. Another type of inhibitor, not shown here, in which Vmax and lselective binding of the inhibitor to the EA complex. 

Allosteric enzymes shift the target enzyme s saturation curve to the left (see p. 92). In Eadie-Hofstee and Lineweaver-Burk plots (see p. 92), allosteric enzymes are recognizable because they produce curved lines (not shown). 

Figure 4.37. Effect of internal transport limitation on Monod-type kinetics demonstrated on a Lineweaver-Burk plot (see Fig. 4.24c) with varied values of a modulus according to Shieh (1980a). The limiting case of no transport limitation is indicated...

Figure 5.10. Demonstration of the four basic types of inhibitions of enzyme kinetics in Lineweaver-Burk plots (see Fig. 4.24c) (a) competitive, (b) noncompetitive, (c) uncompetitive, and (d) substrate inhibition. The parameters and can be estimated from the intercepts and slope of the line with p — 0, where p = inhibitor concentration.

Lineweaver-Burk plot see Kinetic data evaluation. 

Plot both sets of data as a Lineweaver-Burk plot for competitive inhibition (see Fig. 

Almost all enzymes—in contrast to the simplified description given on p. 92—have more than one substrate or product. On the other hand, it is rare for more than two substrates to be bound simultaneously. In bisubstrate reactions of the type A + B C+D, a number of reaction sequences are possible. In addition to the sequential mechanisms (see p.90), in which all substrates are bound in a specific sequence before the product is released, there are also mechanisms in which the first substrate A is bound and immediately cleaved. A part of this substrate remains bound to the enzyme, and is then transferred to the second substrate B after the first product C has been released. This is known as the ping-pong mechanism, and it is used by transaminases, for example (see p.l78). In the Lineweaver— Burk plot (right see p.92), it can be recognized in the parallel shifting of the lines when [B] is varied. 

Effect on Lineweaver-Burke plot Competitive inhibition shows a characteristic Lineweaver-Burke plot in which the plots of the inhibited and uninhibited reactions intersect on the y axis at 1/Vmax (Vmax is unchanged). The inhibited and uninhibited reactions show different x axis intercepts, indicating that the apparent Km is increased in the presence of the competitive inhibitor (see Figure 5.12). 

Effect on Lineweaver-Burke plot Noncompetitive inhibition is readily differentiated from competitive inhibition by plotting 1/v0 versus 1/[S] and noting that Vmax decreases in the presence of a noncompetitive inhibitor, whereas Km is unchanged (see Figure 5.14). 

Light absorption 122,123. See also Absorption spectra of DNA 209 Lily, genome 12 Lineweaver-Burk plot 460 Link protein 181 Linkage between genes 18 Linoleic acid 381 Lipase(s) 634 - 637... 

The value of K, is equal to the concentration of a competitive inhibitor which gives an apparent doubling of the value of Km. Graphically, a form of the Lineweaver-Burk plot"7 is used (see Section 5.4.6). ... 

Repeat Question 11, but graph the data as a linear, double reciprocal plot in the spirit of the Lineweaver-Burk equation (see Chapter 4). Plot l/ATm vs. 1 /(N/nt) and perform a linear regression to determine the best-fit line (Equation 4.a). The x-intercept corresponds to the KD of the DNA-netropsin complex. The KD value from this method should be more accurate than the estimation in Question 11. 

Note that Vmax and Km may be estimated from data on steady state flux and substrate concentration based on a number of different ways of plotting J and [S], Cornish-Bowden illustrates that the Lineweaver-Burk plot (or double-reciprocal plot) is not recommended when one would like to minimize the effect of experimental error on parameter estimates. For a detailed discussion see Section 2.6 of [35]. 

The inhibitor constants, Kj, may be determined by measuring the variation of v with [S] at different concentrations of the inhibitor. Lineweaver—Burk plots can then be used to find K/ from measurements made in the presence, and absence, of inhibitor (see Fig. 2 and Table I). The kinetics of the inhibition of such enzymes as alpha-amylase, hefo-amylase, and phosphorylase have been studied, and inhibitor constants evaluated. 

A noncompetitive inhibitor is usually structurally different ft om the substrate. It is assumed to bind at a site on the enzyme molecule that is different from the substrate-binding site thus, there is no competition between inhibitor and substrate, and a ternary enzyme-inhibitor-substrate (ESI) complex forms. Attachment of the inhibitor to the enzyme does not alter the affinity of the enzyme for its substrate (i.e., K , is unaltered) but the ESI complex does not break down to give products. Since the substrate does not compete with the inhibitor for binding sites on the enzyme molecule, increasing the substrate concentration does not overcome the effect of a noncompetitive inhibitor. Thus Vinax is reduced in the presence of such an inhibitor, whereas K is not altered, as the Lineweaver-Burk plot shows (see Figure 8-9). 

Recently, Ha et al. (2005) reported the inhibitory potentials of JV,Ar-unsubsti-tuted selenourea derivatives 5-8 on tyrosinase. Three types of Ar,AT-unsubsti-tuted selenourea derivatives exhibited an inhibitory effect on the DOPAoxi-dase activity of mushroom tyrosinase. For the structures of these selenourea derivatives (5-8), see Fig. 4. Compound 8 exhibited 55.5% inhibition at a concentration of 200 xM (ICso = 170 xM). This inhibitory effect was higher than that of reference compound kojic acid (39.4%, for structure see Fig. 1) [44]. Interestingly, this compound (8) was identified as a noncompetitive inhibitor by Lineweaver-Burk plot analysis. In addition, 8 also inhibited melanin production in melan-a cells [44]. 

From the Lineweaver-Burk plot (Figure 7-10), we see that as the inhibitor (/) concentration is increased the slope increases (i.e., the rate decreases) while the intercept remains fixed. 

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