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The glycine decarboxylase system: a fascinating complex.
R Douce1, J Bourguignon, M Neuburger
1Département de Biologie Moléculaire et Structurale, Physiologie cellulaire végétale, CEA Grenoble, CNRS et Université Joseph Fourier, 17 rue des martyrs, F 38054 Grenoble, Cedex 9, France. douce@cea.fr
Trends in Plant Science
|April 5, 2001
Summary
The mitochondrial glycine decarboxylase system rapidly breaks down glycine during photorespiration. This crucial enzyme complex, vital for plant energy, is highly concentrated in leaf mitochondria.
Area of Science:
- Biochemistry
- Plant Physiology
- Mitochondrial Metabolism
Background:
- Photorespiration involves the rapid release of glycine from peroxisomes.
- Mitochondria contain a glycine decarboxylase (GDC) multienzyme system linked to serine hydroxymethyltransferase (SHMT) via tetrahydrofolate (THF).
- This system is highly concentrated in the mitochondrial matrix of green leaves.
Purpose of the Study:
- To discuss the structure, mechanism, and biogenesis of the glycine decarboxylase multienzyme system.
- To highlight the pivotal role of the lipoate-dependent H-protein in the GDC catalytic cycle.
- To examine the capacity of plant mitochondria for de novo synthesis of essential cofactors.
Main Methods:
- Review of existing literature on glycine decarboxylase structure and function.
- Analysis of the catalytic mechanism, focusing on the H-protein's role.
- Discussion of cofactor synthesis pathways within plant mitochondria.
Main Results:
- The GDC system comprises P-, H-, T-, and L-proteins, catalyzing glycine breakdown.
- The H-protein acts as a mobile substrate, shuttling between other enzymes.
- Plant mitochondria can synthesize tetrahydrofolate and lipoic acid de novo.
Conclusions:
- The glycine decarboxylase system is essential for managing glycine flux during photorespiration.
- The H-protein is central to the GDC complex's catalytic efficiency.
- Plant mitochondria possess self-sufficiency in producing key cofactors for GDC and SHMT.