Isolation and purification of protein responsible for the conversion of dimethylallylpyrophosphate from poplar leaves into isoprene

The protein converting dimethylallylpyrophosphate (DMAPP) into isoprene ill vitro was isolated and purified 3000-fold from leaves of berry-bearing pop lar (Populus deltoides Marsh.). As the enzyme was purified, its specific ac tivity increased and at the final stage reached 266 nmol/(min mg protein). The enzyme was eluted by anion-exchange chromatography in a 120-170 mM NaCl gradient and by chromatography on the hydroxyapatite column in 170 mM sodi um phosphate. The active molecular weight of the protein determined by gel filtration was 100-110 kD. As the enzyme was purified, the KM value increas ed from 2 to 9 mM. A parallelism isoprene emission from DMAPP and an increa se in the specific activity of the enzyme as it was purified proved that th e enzyme catalyzed isoprene emission.