Table 1. Comparison of the main kinetic and thermodynamic parameters describing the inhibition of PDF by actinonin.

Parameter	AtPDFa	EcPDFa	BsPDF2a , b
K I (nM)d	140±10	112±10	185±15
K I* (nM)c	0.9±0.5	1.3±0.2	2.9±0.8
K I/K I*	155±15	86±10	64±7
k 5 (s−1) ×103d	63±9	170±20	72±8
k 6 (s−1) ×104d	4±1	19±2	11±3
k4 (s−1)e	140±10	112±10	185±15
t1/2 (min)f	29±5	6±1	1.1±0.2

^aThe enzyme concentrations used in the assay were 100, 50, and 25 nM for AtPDF, EcPDF, and BsPDF2, respectively.

^bData from [49].

^cPrior to kinetic analysis for determination of the K _I* value, actinonin was incubated at the final concentration in the presence of the studied enzyme set for 10 min at 37°C. The kinetic assay was initiated by the addition of a small volume of the substrate.

^dFor determination of K _I, k ₅, and k ₆ values, actinonin was not preincubated with the enzyme. The kinetic assay was initiated by the addition of the enzyme.

^e k₄ corresponds to the kinetic constant of the dissociation of the primary enzyme-actinonin complex. It is assumed that the rate of complex association is diffusion-limited (see Table 7.3 in [19]), that is, k₃—the kinetic constant of the association of the primary enzyme-actinonin complex—is 10^{9 M−1}.s⁻¹.

^f t_1/2 is 0.693(k₄+k₅+k₆)/k₄k₆ (see case of induced fit and calculation in Table 1 of [12]). In this case, t_1/2∼0.693/k₆ because k₆<<k₅<<k₄.