Kinetic analysis of urea-inactivation of β-galactosidase in the presence of galactose

Figures & data

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Figure 1 Kinetics of the inactivation of β-galactosidase in the absence and presence of 5 Murea at 50°C,pH 4.5, and at different concentrations of substrate, PNPG, [0.025–0.40 mM] a: In the absence of urea (No urea); b: in the presence of 5 M urea; c: in the presence of 5 Murea and 5 mM galactose; d: in the presence of 5 M urea and 10 mM galactose; e: in the presence of 5 M urea and 20 mM galactose; f: in the presence of 5 M urea and 50 mM galactose.

Figure 2 Effect of urea and galactose on the K_m of β-Galactosidase using pNPG as substrate. a: urea only b: in the presence of 5 M urea and galactose. K_m was calculated from Lineweaver-Burk plots of initial velocity data at the concentrations of urea and galactose indicated.

Figure 3 Semilogarithmic plot of P(μM) vs time (t) of data in Figure 1. a: ln([P]a-[P]t) vs t for 5 M Urea. b: ln([P]a-[P]t) vs t for 5 M Urea,10 mMGalactose. N.B: [P]a = [pNP]; [P]t = [pNP]t.

Figure 4 Plot of apparent inactivation rate constant A against substrate (pNPG) concentration. ai: In the presence of 5 M urea only; aii: In the presence of 5 M Urea and10 mM galactose.(b) A vs [galactose].

Figure 5 Plots of [P]_∞ against [S] for β-galactosidase in the presence of 5 M urea and a: 5 mM galactose b: 10 mM galactose c: 20 mM galactose d: 50 mM galactose.

Figure 6 Plot of k + 0, k′+0 vs [Galactose]. k₊₀ and k′₊₀ being the microscopic inactivation rate constant for the free enzyme and enzyme-substrate complex respectively.

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