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Related Experiment Videos

Carrot cells detoxify N-phosphonoacetyl-L-aspartate by esterification.

S C Cole1, R J Yon

  • 1School of Biological Sciences and Environmental Health, Thames Polytechnic, London, U.K.

The Biochemical Journal
|November 1, 1988
PubMed
Summary

Carrot cells detoxify N-phosphonoacetyl-L-aspartate (PALA) by forming carboxylic esters, a unique tolerance mechanism not seen in other cells. This detoxification process involves specific enzymatic modifications of PALA.

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Area of Science:

  • Biochemistry
  • Plant Physiology
  • Enzymology

Background:

  • Pyrimidine biosynthesis is crucial for cell growth.
  • N-phosphonoacetyl-L-aspartate (PALA) is a known inhibitor of pyrimidine biosynthesis.
  • Carrot cells exhibit unique tolerance to PALA compared to bacterial and mammalian cells.

Purpose of the Study:

  • To elucidate the detoxification mechanism of PALA in carrot cells.
  • To identify the chemical modifications involved in PALA tolerance.
  • To investigate the specificity of the detoxification process.

Main Methods:

  • Anion-exchange chromatography for isolating detoxified PALA.
  • Incubation with carboxylic-ester hydrolase to assess enzyme activity.
  • Gas-liquid chromatography (G.1.c.) analysis of hydrolysis products.

Related Experiment Videos

  • Comparative studies with succinate to determine specificity.

    • Main Results:

    • Carrot cells detoxify PALA by forming carboxylic esters, altering its charge.
    • Enzymatic hydrolysis of detoxified PALA with carboxylic-ester hydrolase restored its inhibitory activity.
    • G.1.c. analysis revealed the formation of mono- and di-carboxylic esters (methyl and ethyl).
    • The detoxification mechanism demonstrated high specificity for PALA, not affecting succinate.

    Conclusions:

    • Carrot cell PALA tolerance is mediated by esterification, a novel detoxification pathway.
    • The formation of carboxylic esters is the key step in PALA detoxification.
    • The observed specificity suggests a targeted enzymatic process for PALA metabolism in carrots.