The glycine decarboxylase system: a fascinating complex.
The mitochondrial glycine decarboxylase multienzyme system, connected to serine hydroxymethyltransferase through a soluble pool of tetrahydrofolate, consists of four different component enzymes, the P-, H-, T- and L-proteins. In a multi-step reaction, it catalyses the rapid destruction of glycine molecules flooding out of the peroxisomes during the course of photorespiration. In green leaves, this multienzyme system is present at tremendously high concentrations within the mitochondrial matrix. The structure, mechanism and biogenesis of glycine decarboxylase are discussed. In the catalytic cycle of glycine decarboxylase, emphasis is given to the lipoate-dependent H-protein that plays a pivotal role, acting as a mobile substrate that commutes successively between the other three proteins. Plant mitochondria possess all the necessary enzymatic equipment for de novo synthesis of tetrahydrofolate and lipoic acid, serving as cofactors for glycine decarboxylase and serine hydroxymethyltransferase functioning.
Douce
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Département 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
Bourguignon
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Neuburger
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Rébeillé
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D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D019069:Cell Respiration; D005998:Glycine / Q000378:metabolism; D050961:Glycine Decarboxylase Complex H-Protein; D050841:Glycine Dehydrogenase (Decarboxylating); D012696:Glycine Hydroxymethyltransferase / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D020675:Peroxisomes / Q000378:metabolism; D010944:Plants / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D013763:Tetrahydrofolates / Q000378:metabolism
D050961:Glycine Decarboxylase Complex H-Protein; D009097:Multienzyme Complexes; D013763:Tetrahydrofolates; C030371:5,6,7,8-tetrahydrofolic acid; D000594:Amino Acid Oxidoreductases; D050841:Glycine Dehydrogenase (Decarboxylating); D012696:Glycine Hydroxymethyltransferase; D005998:Glycine