Abstract
Transfer of 3H from d-gluconic acid, specifically labelled with 3H at C-2 or C-3 and 14C at C-1, C-2, or C-3, 4, to l(+)-tartaric acid was examined in leaves and berries of Vitis labrusca cv Delaware and in leaves of Parthenocissus quinquefolia. 3H located at C-3 of d-gluconic acid was highly conserved in this transfer, yielding a 3H/ 14C ratio between 3.3 and 14 in the light and between 11 and 22 in the dark. These experiments strongly suggest that a portion of the 3H present in l(+)-tartaric acid may have been transferred from d-gluconic acid to l(+)-tartaric acid, possibly via NADP[ 3H] through a redox process involving reduction of l- xylo-2-hexulosonate (2-keto- l-idonate). Both [ 3H]tartaric acid and [ 14C]tartaric acid synthesized in grape leaves from d-[3- 3H, 2- 14C]gluconic acid, or [3- 3H, 3,4- 14C]gluconic acid were characterized as l(+)-chiral form exclusively, the naturally occurring form of tartaric acid.
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