Metabolism of l-Threonic Acid in Rumex x acutus L. and Pelargonium crispum (L.) L'Hér 1

AUTOR(ES)

Helsper, Johannes P.

RESUMO

l-Threonic acid is a natural constituent in leaves of Pelargonium crispum (L.) L'Hér (lemon geranium) and Rumex x acutus L. (sorrel). In both species, l-[14C]threonate is formed after feeding l-[U-14C]ascorbic acid to detached leaves. R. acutus leaves labeled with l-[4-3H]- or l-[6-3H]ascorbic acid produce l-[3H]threonate, in the first case internally labeled and in the second case confined to the hydroxymethyl group. These results are consistent with the formation of l-threonate from carbons three through six of l-ascorbic acid. Detached leaves of P. crispum oxidize l-[U-14C] threonate to l-[14C]tartrate whereas leaves of R. acutus produce negligible tartrate and the bulk of the 14C appears in 14CO2, [14C]sucrose, and other products of carbohydrate metabolism. R. acutus leaves that are labeled with l-[U-14C]threonate release 14CO2 at linear rate until a limiting value of 25% of the total [U-14C]threonate is metabolized. A small quantity of [14C]glycerate is also produced which suggests a process involving decarboxylation of l-[U-14C]threonate.

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