The metabolism of L-[6-14C]ascorbic acid in detached grape leaves1

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Abstract
Grape leaves (Vitis labrusca L.) that are removed from the position opposite the flower cluster either 28 or 14 days before anthesis cleave L-ascorbic acid (AA) at the C4-C5 bond into a C4 and, presumably, a C2 fragment. Leaves taken from this position 14 days after anthesis fail to cleave AA. The C4 fragment is utilized for L(+)-tartaric acid (TA) biosynthesis while the C2 fragment is recycled into hexose and products of the hexose metabolism. When [6-14C]AA is the source of the label, the sucrose-derived glucose from labeled leaves has a distribution of 14C in the carbon skeleton as follows: Cl, 35%; C2, 14%; C3, 4%; C(4+5), 13% and C6, 34%. The effect of inhibitors of the glycolate pathway on [6-l4C]AA metabolism is examined.