Steady-state kinetics of thyroid peroxidase. Evidence for a high degree rate equation using the F statistic.

The initial-rate kinetics of bovine thyroid peroxidase are reported using 325 sets of concentrations of hydrogen peroxide and guaiacol. Extended ranges of concentrations are used and the v(S) profiles are fitted by rational functions of degree 2:2, 3:3 and +:4 by interactive non-linear regression analysis. Estimates of initial slopes in v(S) plots obtained by this regression are then replotted against the fixed substrate concentration and this confirms the need for a high-degree rate equation. Values of the F statistic indicate that the rate equation is 3:3 in guaiacol and 4:4 in hydrogen peroxide. It is concluded that the kinetics of peroxidase from bovine thyroid, like horse radish and human cervical mucus peroxidase and lactoperoxidase can be accommodated by the greater cyclic mechanism and that this is the minimal kinetic scheme for peroxidase In general.