Lanosterol 14α-demethylase. The metabolism of some potential intermediates by cell-free systems from rat liver

Abstract A number of potential intermediates of lanosterol ∗ 14α-demethylation have been synthesized for the first time and labelled with 3 H. A direct comparison of the rates of conversion of each of these materials to cholesterol and 5α-cholest-7-en-3β-ol by a cell-free system from rat liver has been made. Although 5α-lanost-8-en-3β,32-diol and 3β-hydroxy-5α-lanost-8-en-32-al were converted to C 27 sterols at a greater rate than was 5α-lanost-8-en-3β-ol, the apparent K m values were larger than those expected if these compounds were obligatory intermediates. 5α-Lanost-8-en-3β,15α-diol and 5α-lanost-8-en-3β,15β-diol were poorer precursors of cholesterol but each was extensively converted both to a more polar compound and to the corresponding 3β,15-diol diester.