A high affinity pyruvate decarboxylase is present in cottonwood leaf veins and petioles

A second source of leaf acetaldehyde emission?

T. Nguyen, A. M. Drotar, Russell Monson, R. Fall

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Considerable evidence indicates that acetaldehyde is released from the leaves of a variety of plants. The conventional explanation for this is that ethanol formed in the roots is transported to the leaves where it is converted to acetaldehyde by the alcohol dehydrogenase (ADH) found in the leaves. It is possible that acetaldehyde could also be formed in leaves by action of pyruvate decarboxylase (PDC), an enzyme with an uncertain metabolic role, which has been detected, but not characterized, in cottonwood leaves. We have found that leaf PDC is present in leaf veins and petioles, as well as in non-vein tissues. Veins and petioles contained measurable pyruvate concentrations in the range of 2 mM. The leaf vein form of the enzyme was purified approximately 143-fold, and, at the optimum pH of 5.6, the Km value for pyruvate was 42 μM. This Km is lower than the typical millimolar range seen for PDCs from other sources. The purified leaf PDC also decarboxylates 2-ketobutyric acid (Km = 2.2 mM). We conclude that there are several possible sources of acetaldehyde production in cottonwood leaves: the well-characterized root-derived ethanol oxidation by ADH in leaves, and the decarboxylation of pyruvate by PDC in leaf veins, petioles, and other leaf tissues. Significantly, the leaf vein form of PDC with its high affinity for pyruvate, could function to shunt pyruvate carbon to the pyruvate dehydrogenase by-pass and thus protect the metabolically active vascular bundle cells from the effects of oxygen deprivation.

Original languageEnglish (US)
Pages (from-to)1217-1221
Number of pages5
JournalPhytochemistry
Volume70
Issue number10
DOIs
StatePublished - Jul 2009
Externally publishedYes

Fingerprint

Pyruvate Decarboxylase
pyruvate decarboxylase
Populus
Acetaldehyde
acetaldehyde
plant veins
petioles
Pyruvic Acid
Veins
leaves
Alcohol Dehydrogenase
Ethanol
Tissue
alcohol dehydrogenase
Decarboxylation
pyruvate dehydrogenase (lipoamide)
Enzymes
ethanol
Blood Vessels
Oxidoreductases

Keywords

  • Acetaldehyde
  • Eastern cottonwood
  • Enzyme purification
  • Petioles
  • Populus deltoides
  • Pyruvate decarboxylase
  • Pyruvic acid
  • Vascular bundles
  • Veins

ASJC Scopus subject areas

  • Plant Science
  • Biochemistry
  • Molecular Biology
  • Horticulture

Cite this

A high affinity pyruvate decarboxylase is present in cottonwood leaf veins and petioles : A second source of leaf acetaldehyde emission? / Nguyen, T.; Drotar, A. M.; Monson, Russell; Fall, R.

In: Phytochemistry, Vol. 70, No. 10, 07.2009, p. 1217-1221.

Research output: Contribution to journalArticle

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abstract = "Considerable evidence indicates that acetaldehyde is released from the leaves of a variety of plants. The conventional explanation for this is that ethanol formed in the roots is transported to the leaves where it is converted to acetaldehyde by the alcohol dehydrogenase (ADH) found in the leaves. It is possible that acetaldehyde could also be formed in leaves by action of pyruvate decarboxylase (PDC), an enzyme with an uncertain metabolic role, which has been detected, but not characterized, in cottonwood leaves. We have found that leaf PDC is present in leaf veins and petioles, as well as in non-vein tissues. Veins and petioles contained measurable pyruvate concentrations in the range of 2 mM. The leaf vein form of the enzyme was purified approximately 143-fold, and, at the optimum pH of 5.6, the Km value for pyruvate was 42 μM. This Km is lower than the typical millimolar range seen for PDCs from other sources. The purified leaf PDC also decarboxylates 2-ketobutyric acid (Km = 2.2 mM). We conclude that there are several possible sources of acetaldehyde production in cottonwood leaves: the well-characterized root-derived ethanol oxidation by ADH in leaves, and the decarboxylation of pyruvate by PDC in leaf veins, petioles, and other leaf tissues. Significantly, the leaf vein form of PDC with its high affinity for pyruvate, could function to shunt pyruvate carbon to the pyruvate dehydrogenase by-pass and thus protect the metabolically active vascular bundle cells from the effects of oxygen deprivation.",
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T1 - A high affinity pyruvate decarboxylase is present in cottonwood leaf veins and petioles

T2 - A second source of leaf acetaldehyde emission?

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AU - Monson, Russell

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AB - Considerable evidence indicates that acetaldehyde is released from the leaves of a variety of plants. The conventional explanation for this is that ethanol formed in the roots is transported to the leaves where it is converted to acetaldehyde by the alcohol dehydrogenase (ADH) found in the leaves. It is possible that acetaldehyde could also be formed in leaves by action of pyruvate decarboxylase (PDC), an enzyme with an uncertain metabolic role, which has been detected, but not characterized, in cottonwood leaves. We have found that leaf PDC is present in leaf veins and petioles, as well as in non-vein tissues. Veins and petioles contained measurable pyruvate concentrations in the range of 2 mM. The leaf vein form of the enzyme was purified approximately 143-fold, and, at the optimum pH of 5.6, the Km value for pyruvate was 42 μM. This Km is lower than the typical millimolar range seen for PDCs from other sources. The purified leaf PDC also decarboxylates 2-ketobutyric acid (Km = 2.2 mM). We conclude that there are several possible sources of acetaldehyde production in cottonwood leaves: the well-characterized root-derived ethanol oxidation by ADH in leaves, and the decarboxylation of pyruvate by PDC in leaf veins, petioles, and other leaf tissues. Significantly, the leaf vein form of PDC with its high affinity for pyruvate, could function to shunt pyruvate carbon to the pyruvate dehydrogenase by-pass and thus protect the metabolically active vascular bundle cells from the effects of oxygen deprivation.

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