Abstract
Squalene synthetase of pig liver has been solubilized and partially purified. This enzyme has a pH optimum of 7.4 and a K m value of 5 × 10 −7 M for farnesyl pyrophosphate. A divalent metal ion, Mg ++ or Mn ++, and NADPH are required for the conversion of farnesyl pyrophosphate to squalene. Inhibition of the reaction is effected in the presence of nerolidyl pyrophosphate and SH inhibitors. Inhibition is also effected by farnesyl pyrophosphate at concentrations greater than 1.0 × 10 −4 M. Farnesyl pyrophosphate reacts with the enzyme to form an enzyme bound intermediate (C 15) with the release of pyrophosphate. A C 30-enzyme compound has also been isolated and this compound has been converted to squalene on addition of NADPH and Mg ++ to the incubation mixture. A mechanism for the conversion of farnesyl pyrophosphate to squalene has been proposed from these findings.
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