Metabolism of l-Threonic Acid in Rumex x acutus L. and Pelargonium crispum (L.) L'Hér.
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Journal: 2010/June - Plant Physiology
ISSN: 0032-0889
PUBMED: 16662405
Abstract:
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-[(14)C]threonate is formed after feeding l-[U-(14)C]ascorbic acid to detached leaves. R. acutus leaves labeled with l-[4-(3)H]- or l-[6-(3)H]ascorbic acid produce l-[(3)H]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-(14)C] threonate to l-[(14)C]tartrate whereas leaves of R. acutus produce negligible tartrate and the bulk of the (14)C appears in (14)CO(2), [(14)C]sucrose, and other products of carbohydrate metabolism. R. acutus leaves that are labeled with l-[U-(14)C]threonate release (14)CO(2) at linear rate until a limiting value of 25% of the total [U-(14)C]threonate is metabolized. A small quantity of [(14)C]glycerate is also produced which suggests a process involving decarboxylation of l-[U-(14)C]threonate.
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Plant Physiol 69(6): 1365-1368
PMID: 16662405

Metabolism of <span class="small-caps">l</span>-Threonic Acid in <em>Rumex x acutus</em> L. and <em>Pelargonium crispum</em> (L.) L'Hér <sup><a href="#fn1" rid="fn1" class=" fn">1</a></sup>

Abstract

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-[C]threonate is formed after feeding l-[U-C]ascorbic acid to detached leaves. R. acutus leaves labeled with l-[4-H]- or l-[6-H]ascorbic acid produce l-[H]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-C] threonate to l-[C]tartrate whereas leaves of R. acutus produce negligible tartrate and the bulk of the C appears in CO2, [C]sucrose, and other products of carbohydrate metabolism. R. acutus leaves that are labeled with l-[U-C]threonate release CO2 at linear rate until a limiting value of 25% of the total [U-C]threonate is metabolized. A small quantity of [C]glycerate is also produced which suggests a process involving decarboxylation of l-[U-C]threonate.

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Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164
To whom inquiries and requests for reprints should be addressed.
Supported by grants from the National Institutes of Health (GM-22427), the National Science Foundation (PCM-7813254), and the Netherlands Organization for the Advancement of Pure Research (Z. W. O.). Scientific paper No. 6075, Project 0266, College of Agriculture Research Center, Washington State University, Pullman, WA 99164.
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Abstract
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-[C]threonate is formed after feeding l-[U-C]ascorbic acid to detached leaves. R. acutus leaves labeled with l-[4-H]- or l-[6-H]ascorbic acid produce l-[H]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-C] threonate to l-[C]tartrate whereas leaves of R. acutus produce negligible tartrate and the bulk of the C appears in CO2, [C]sucrose, and other products of carbohydrate metabolism. R. acutus leaves that are labeled with l-[U-C]threonate release CO2 at linear rate until a limiting value of 25% of the total [U-C]threonate is metabolized. A small quantity of [C]glycerate is also produced which suggests a process involving decarboxylation of l-[U-C]threonate.
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