Lysozyme rate enhancement

Bell-shaped pH-rate profiles are obtained in lysozyme reactions (Rupley et al., 1967) which are consistent with direct involvement of two groups in the reaction. However, bell-shaped pH-rate constant profiles are also observed in the hydrolysis of benzaldehyde disalicyl acetals, and in the case of p-nitrobenzaldehyde o-carboxyphenyl p-carboxyphenyl acetal only one carboxyl group can participate. One should then take care in postulating bifunctional catalysis in the lysozyme reaction, since the observed kinetics and the rate enhancements are explicable in terms of a chemically simpler mechanism (general acid catalysis by glutamic acid-35 along with release of ground state... 

Some of the observed LIS values and relaxation rate enhancements of CH resonances of hen egg white lysozyme with various lanthanides [108] are given in Table 10.9. 

Most of the quantitative work in this area has been done with putative models for lysozyme action. Thus, synchronous acetamido group participation and intramolecular general acid catalysis was held to be responsible for the modest rate enhancement of compound LXI compared with the p-nitrophenyl compound or salicyl glucoside... 

Fig. 24.2. Single-molecule recording of T4 lysozyme conformational motions and enzymatic reaction turnovers of hydrolysis of an E. coli B cell wall in real time, (a) This panel shows a pair of trajectories from a fluorescence donor tetramethyl-rhodamine blue) and acceptor Texas Red (red) pair in a single-T4 lysozyme in the presence of E. coli cells of 2.5mg/mL at pH 7.2 buffer. Anticorrelated fluctuation features are evident. (b) The correlation functions (C (t)) of donor ( A/a (0) Aid (f)), blue), acceptor ((A/a (0) A/a (t)), red), and donor-acceptor cross-correlation function ((A/d (0) A/d (t)), black), deduced from the single-molecule trajectories in (a). They are fitted with the same decay rate constant of 180 40s. A long decay component of 10 2s is also evident in each autocorrelation function. The first data point (not shown) of each correlation function contains the contribution from the measurement noise and fluctuations faster than the time resolution. The correlation functions are normalized, and the (A/a (0) A/a (t)) is presented with a shift on the y axis to enhance the view, (c) A pair of fluorescence trajectories from a donor (blue) and acceptor (red) pair in a T4 lysozyme protein without substrates present. The acceptor was photo-bleached at about 8.5 s. (d) The correlation functions (C(t)) of donor ((A/d (0) A/d (t)), blue), acceptor ((A/a (0) A/a (t)), red) derived from the trajectories in (c). The autocorrelation function only shows a spike at t = 0 and drops to zero at t > 0, which indicates that only uncorrelated measurement noise and fluctuation faster than the time resolution recorded (Adapted with permission from [12]. Copyright 2003 American Chemical Society)...

The dynamic surface tension measurements performed in phosphate buffer solutions (pH 6.0,1 = 0.05 M) at constant lysozyme concentration, 5.1x10 M, and varying concentrations of MR, show that the LYS-MR mixture is characterized by more high rate of adsorption and more low quasi-equilibrium surface tension, than pure LYS (Fig. 1). As concerning the effect of MR on the surface activity of lysozyme, it is seen from Fig. 2 that MR enhances it at all using concentration-making lysozyme more hydrophobic. MR critical micelle concentration in lysozyme presence is 32.7 mM. 

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