SYNTHESIS OF CHLOROPHYLL-A AND BETA-CAROTENE FROM H-2-LABELED AND C-13-LABELED MEVALONATES AND C-13-LABELED GLYCINE IN CULTURED-CELLS OF LIVERWORTS, HETEROSCYPHUS-PLANUS AND LOPHOCOLEA-HETEROPHYLLA
K. Nabeta et al., SYNTHESIS OF CHLOROPHYLL-A AND BETA-CAROTENE FROM H-2-LABELED AND C-13-LABELED MEVALONATES AND C-13-LABELED GLYCINE IN CULTURED-CELLS OF LIVERWORTS, HETEROSCYPHUS-PLANUS AND LOPHOCOLEA-HETEROPHYLLA, Journal of the Chemical Society. Perkin transactions. I, (3), 1997, pp. 261-267
H-2- And C-13-labelled mevalonates (MVA) are incorporated at a higher
rate into the phytyl side-chain of chlorophyll alpha and beta-carotene
than into diterpenes in suspension cultures of liverworts, Heteroscyp
hus planus and Lophocolea heterophylla. The distribution of labels in
the biosynthetically labelled chlorophyll a, phytol and beta-carotene
incorporating MVA determined by H-2 and C-13 NMR analyses indicates pr
eferential labelling of the farnesyl diphosphate (FPP)-derived portion
of these compounds. These findings suggest that all compounds formed
from geranylgeranyl diphosphate within the chloroplasts are biosynthes
ized partly via the condensation of FPP derived from exogenous MVA and
endogenous isopentenyl diphosphate, and that the pigments and normal
diterpenes are biosynthesized separately at different sites within the
chloroplasts. In contrast, [2-C-13]glycine administered to the cultur
ed cells of H. planus equivalently labels both the phytyl side-chain a
nd beta-carotene, indicating that endogenously formed MVA via glycine
is equivalently incorporated both into the phytyl moiety and beta-caro
tene. Intense doublets due to C-13-C-13 coupling, observed in the C-13
-labelled phytyl side-chain and beta-carotene, suggest that acetyl-CoA
is mainly formed from serine derived from 5,10-methylenetetrahydrofol
ic acid and glycine.