Metabolism of tetraorganolead compounds by rat-liver microsomal mono-oxygenase. III. Enzymic dealkylation of tetramethyl lead compared with tetraethyl lead

Abstract

1. The enzymic transformation of tetramethyl lead (PbMe₄) to the trimethyl lead cation is very rapid with sp. activities of 40-50 nmol/min per mg protein. The reaction has an apparent K_m of 1.28 × 10⁻⁵ M.

2. PbMe₄ binds to cytochrome P-450 with a type 1 difference spectrum, K_s is 6.65 × 10⁻⁶M.

3. Comparison of the data with results previously obtained for lead tetraethyl (PbEt₄) shows that the 20 times higher metabolic rates observed with PbMe₄ are related to an intrinsic higher O₂ activation as well as to a more effective O₂ utilization by that substrate.