Fig. 8: Evaluation of the effect of l-Ser as a modifier of the kinetics of phosphoserine (PS) dephosphorylation by MtSerB2 dimer.

a Plots of initial velocities (nmol phosphate released per µg of MtSerB2 per minute) as v/[E]_t (min⁻¹) versus substrate concentration for PS dephosphorylation by MtSerB2 dimer fraction pool at various fixed l-Ser concentrations (µM). Error bars represent the s.d. of three experiments. Plain lines are the fit of the developed form of the general modifier Eq. (2) to the experimental data. b Dependence of the apparent kinetic parameters k_cat, K_M, (k_cat/K_M) on l-Ser concentration. The shape of the plots are designated by a framed letter (as explained in Supplementary Table 1 and https://www.enzyme-modifier.ch) and allows the identification of a mechanism of hyperbolic mixed, predominantly specific inhibition according to the methodology of Baici²⁶. Plain lines are the fits of the dependency of apparent kinetic parameters on [l-Ser] to the experimental data based on the general modifier equation (Eqs. (3–7)). Error bars represent the standard error of the parameter as calculated by Prism following non-linear regression. c General modifier mechanism. E enzyme, S substrate (phosphoserine), P product (phosphate), I inhibitor (l-Ser), k_cat catalytic constant, K_M Michaelis constant, K_i inhibition constant, α reciprocal allosteric coupling constant, β factor by which the modifier affects k_cat. d Plot of initial velocity versus l-Ser concentration at fixed PS concentrations. Source data are available on the FigShare repository (https://doi.org/10.6084/m9.figshare.24116571).