The Purification and Properties of Pig Liver Geranyl Pyrophosphate Synthetase

Abstract

Abstract The purification and properties of geranyl pyrophosphate synthetase are reported. This enzyme is purified simultaneously with the enzyme for the synthesis of farnesyl pyrophosphate. It does not, however, have geranylgeranyl pyrophosphate synthetase activity. This enzyme, obtained as a single band of protein by starch gel electrophoresis, catalyzes the formation of both geranyl and farnesyl pyrophosphates from dimethylallyl pyrophosphate and 4-14C-isopentenyl pyrophosphate. These products have been identified by paper and gas-liquid chromatography. A pH range of 7.0 to 7.8 is optimum for the reaction. A metal ion is required and either Mg++ or Mn++ may be used, but Mn++ inhibits the reaction at concentrations greater than 4 x 10-3 m. Km values for isopentenyl and dimethylallyl pyrophosphates are 1.25 x 10-6 and 2.2 x 10-6 m, respectively. N-Ethylmaleimide and p-chloromercuribenzoate strongly inhibit the synthetase reaction, but iodoacetamide has only a slight inhibitory effect. The s20,w value for the synthetase is 4.7.