Abstract
Comparative substrate specificities of farnesyl pyrophosphate synthetases I and II purified from larvae of silkworm, Bombyx mori, were studied by use of the possible biosynthetic intermediates of juvenile hormones in the insect. In the presence of Mn2+ ions farnesyl pyrophosphate synthetase II showed higher activity than synthetase I and the corresponding enzyme from pig liver with the following substrate homologues: (Z)-3-methyl-2-pentenyl-, 3-ethyl-3-butenyl-, (2E, 6Z)-3, 7-dimethyl-2, 6-nonadienyl-, and (2E, 6Z)-3-ethyl-7-methyl-2, 6-nonadienyl pyrophosphate. When (Z)-3-methyl-2-pentenyl-, 3-ethyl-3-butenyl-, and isopentenyl pyrophosphate were mixed and incubated with farnesyl pyrophosphate synthetase II, (2E, 6E, 10Z)-3, 11-dimethyl-7-ethyl-2, 6, 10-tridecatrienyl-, (2E, 6 E, 10Z)-3, 7, 11-trimethyl-2, 6, 10-tridecatrienyl, and a trace amount of (2E, 6E, 1OZ)-3, 7-diethyl-ll-methyl-2, 6, 10-tridecatrienyl pyrophosphate, whose carbon skeletons were the same as those of juvenile hormone I, II, and O, respectively, were formed.
(Z)-3-Methyl-2-pentenyl pyrophosphate was produced from 3-ethyl-3-butenyl pyrophosphate as a single product by the action of silkworm isopentenyl pyrophosphate isomerase, though the enzyme activity was much lower with this substrate than with the usual substrate, isopentenyl pyrophosphate.
