Studies on the Biosynthesis of Natural Rubber

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Isopentenyl diphosphate (IPP) isomerase [EC 5.3.3.2], which catalyzes the reversible isomerization of IPP to dimethylallyl diphosphate, is presumed to be involved in rubber biosynthesis, but no direct evidence has been given for its occurrence in rubber latex. This enzyme activity was found in the C-serum powder prepared by lyophilization of centrifuged rubber latex of Hevea brasiliensis.In connection with the biosynthesis of rubber, prenyltransferase activities in the C-serum powder were examined. Farnesyl diphosphate (C_<15>) and geranylgeranyl diphosphate (C_<20>) were detected as major products. In addition, a polyprenyl diphosphate (-C_<30>) was obtained when geranyl diphosphate (C_<10>) was employed as the allylic substrate. When the C-serum was chromatographed on DEAE-Toyopearl, several prenyltransferase fractions were obtained. One of the partially purified enzyme fractions showed an activity of producing a polyprenyl product with a chain length longer than C_<80> as well as a C_<15> product.