Related Experiment Videos
Carrot cells detoxify N-phosphonoacetyl-L-aspartate by esterification
1School of Biological Sciences and Environmental Health, Thames Polytechnic, London, U.K.
The Biochemical Journal
|November 1, 1988
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.
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.
- 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.