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Localization and interconversion of tetrahydropteroylglutamates in isolated pea mitochondria
Abstract:
1. Mitochondria were extracted from 4-day-old pea cotyledons and purified on a sucrose density gradient. 2. Microbiological assay of the purified mitochondrial fraction with Lactobacillus casei (A.T.C.C. 7469), Streptococcus faecalis (A.T.C.C. 8043) and Pediococcus cerevisiae (A.T.C.C. 8081) revealed a discrete pool of conjugated and unconjugated derivatives of tetrahydropteroylglutamic acid. 3. Solubilization and chromatographic studies of the mitochondrial fraction demonstrated the presence of formylated and methylated derivatives, 10-formyltetrahydropteroylmonoglutamic acid, 5-formyltetrahydropteroylmonoglutamic acid and 5-formyltetrahydropteroyldiglutamic acid being the major derivatives present. 4. The principal mitochondrial pteroylglutamates were labelled when dry seeds were allowed to imbibe [2-(14)C]pteroylglutamic acid and 5-[methyl-(14)C]-methyltetrahydropteroylmonoglutamic acid. 5. The ability of isolated mitochondria to catalyse oxidation and reduction of tetrahydropteroylglutamic acid derivatives was demonstrated in feeding experiments in which [(14)C]formaldehyde, [3-(14)C]serine, sodium [(14)C]formate, 5-[methyl-(14)C]methyltetrahydropteroylmonoglutamic acid or [2-(14)C]-glycine served as C(1) donor. In addition, (14)C was incorporated into free amino acids related to C(1) metabolism.
Insights
Mitochondria in pea cotyledons contain folate derivatives essential for C1 metabolism. These mitochondria can interconvert folate forms, indicating their role in plant folate processing.
Area of Science:
- Plant biochemistry
- Mitochondrial function
- Folate metabolism
Background:
- Tetrahydropteroylglutamic acid derivatives are crucial in various metabolic pathways.
- Mitochondria play a central role in cellular energy production and metabolic regulation.
- Understanding folate metabolism in plants is vital for agricultural and nutritional science.
Purpose of the Study:
- To investigate the presence and forms of folate derivatives within pea cotyledon mitochondria.
- To determine the metabolic capabilities of isolated pea mitochondria concerning folate compounds.
- To elucidate the role of plant mitochondria in C1 metabolism.
Main Methods:
- Mitochondrial extraction and purification from pea cotyledons using sucrose density gradient.
- Microbiological assays with specific bacterial strains to quantify folate derivatives.
- Solubilization and chromatographic techniques to identify and characterize folate compounds.
- Isotope labeling studies using radiolabeled precursors to trace folate metabolism.
- In vitro experiments to assess mitochondrial enzymatic activity in folate interconversion.
Main Results:
- Purified pea mitochondria contain a distinct pool of conjugated and unconjugated tetrahydropteroylglutamic acid derivatives.
- Formylated and methylated folate derivatives, including 10-formyltetrahydropteroylmonoglutamic acid and 5-formyltetrahydropteroylmonoglutamic acid, were identified as major forms.
- Mitochondria demonstrated the capacity to catalyze oxidation and reduction reactions of tetrahydropteroylglutamic acid derivatives.
- Isotopic labeling confirmed the incorporation of C1 units into mitochondrial folates and related amino acids.
Conclusions:
- Pea cotyledon mitochondria possess unique folate derivatives involved in C1 metabolism.
- Isolated mitochondria are capable of interconverting various folate forms, highlighting their metabolic significance.
- These findings contribute to a deeper understanding of folate biochemistry and C1 metabolism in plants.