From Aspartate to Ethylene:
Central Role of N, C, and S Shuttles
by Aminotransferases During Biosynthesis
of a Major Plant Growth Hormone
E. Le Deunff
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
2 A Highly Regulated Pathway for the Biosynthesis of Methionine
and S-Adenosylmethionine (AdoMet): The Ethylene Precursors . . . . . . . . . . . . . . . . . . . . . . . . . . 256
2.1 Glutamine Involvement in the Methionine Pathway Is Hidden Behind the PLP
Coenzyme Used by Aminotransferases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
2.2 Serine Is Doubly Implicated in Methionine Biosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
2.3 AdoMet Synthase Is a Fundamental Control Point of the Methionine Pathway . . . . 261
3 Because of Its Vital Cellular Functions AdoMet Requires Two Salvage Pathways . . . . . . . 262
3.1 A Methyl Cycle Serves to Regenerate the Methyl Group Issued from AdoMet . . . . 263
3.2 Ethylene and Polyamines Are By-Products Resulting from the Recycling
of the Methylthio-Group of MTA Issued from AdoMet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
4 ACS and SAMDC Are Key Enzymes in Ethylene and Polyamine Biosynthetic Pathways
and MTA Recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
4.1 SAMDC Is the Rate-Limiting Step for Polyamine Biosynthesis . . . . . . . . . . . . . . . . . . . . 265
4.2 ACS Aminotransferase Is the Rate-Limiting Step for Ethylene Biosynthesis . . . . . . . 266
4.3 Cytosolic Levels of ACC Can Be Modulated in Many Ways . . . . . . . . . . . . . . . . . . . . . . . 267
4.4 Are ACC and Polyamines Potential Ligands or Modulators of Plant Glutamate
Receptors? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
5 Relationship Between Ethylene and N Metabolism: The Central Role
of Aminotransferases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
5.1 Methionine and Tryptophan Interconversion by VAS1 and TAA Aminotransferases 272
5.2 Methionine and Phenylalanine Interconversion by PPY-AT in the New
Phenylpyruvate Pathway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
5.3 In Search of the Last Missing Aminotransferase to Complete the Yang Cycle . . . . . 273
5.4 Is Tryptophan Aminotransferase Also Involved in Histidine Catabolism? . . . . . . . . . . 274
6 Use of Olefinic Glycine Inhibitors in Ethylene Biosynthesis: The Devious Trap . . . . . . . . . 275
6.1 In Search for Highly Specific Inhibitors of ACS and TAA Aminotransferases . . . . . 276
E. Le Deunff (*)
Normandie Université, UNICAEN, ICORE, Caen, France
e-mail: erwan.ledeunff@unicaen.fr
© Springer International Publishing AG 2018
Progress in Botany (2019) 80: 253–294, DOI 10.1007/124_2018_17,
Published online: 28 February 2018
253
Central Role of N, C, and S Shuttles
by Aminotransferases During Biosynthesis
of a Major Plant Growth Hormone
E. Le Deunff
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
2 A Highly Regulated Pathway for the Biosynthesis of Methionine
and S-Adenosylmethionine (AdoMet): The Ethylene Precursors . . . . . . . . . . . . . . . . . . . . . . . . . . 256
2.1 Glutamine Involvement in the Methionine Pathway Is Hidden Behind the PLP
Coenzyme Used by Aminotransferases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
2.2 Serine Is Doubly Implicated in Methionine Biosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
2.3 AdoMet Synthase Is a Fundamental Control Point of the Methionine Pathway . . . . 261
3 Because of Its Vital Cellular Functions AdoMet Requires Two Salvage Pathways . . . . . . . 262
3.1 A Methyl Cycle Serves to Regenerate the Methyl Group Issued from AdoMet . . . . 263
3.2 Ethylene and Polyamines Are By-Products Resulting from the Recycling
of the Methylthio-Group of MTA Issued from AdoMet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
4 ACS and SAMDC Are Key Enzymes in Ethylene and Polyamine Biosynthetic Pathways
and MTA Recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
4.1 SAMDC Is the Rate-Limiting Step for Polyamine Biosynthesis . . . . . . . . . . . . . . . . . . . . 265
4.2 ACS Aminotransferase Is the Rate-Limiting Step for Ethylene Biosynthesis . . . . . . . 266
4.3 Cytosolic Levels of ACC Can Be Modulated in Many Ways . . . . . . . . . . . . . . . . . . . . . . . 267
4.4 Are ACC and Polyamines Potential Ligands or Modulators of Plant Glutamate
Receptors? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
5 Relationship Between Ethylene and N Metabolism: The Central Role
of Aminotransferases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
5.1 Methionine and Tryptophan Interconversion by VAS1 and TAA Aminotransferases 272
5.2 Methionine and Phenylalanine Interconversion by PPY-AT in the New
Phenylpyruvate Pathway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
5.3 In Search of the Last Missing Aminotransferase to Complete the Yang Cycle . . . . . 273
5.4 Is Tryptophan Aminotransferase Also Involved in Histidine Catabolism? . . . . . . . . . . 274
6 Use of Olefinic Glycine Inhibitors in Ethylene Biosynthesis: The Devious Trap . . . . . . . . . 275
6.1 In Search for Highly Specific Inhibitors of ACS and TAA Aminotransferases . . . . . 276
E. Le Deunff (*)
Normandie Université, UNICAEN, ICORE, Caen, France
e-mail: erwan.ledeunff@unicaen.fr
© Springer International Publishing AG 2018
Progress in Botany (2019) 80: 253–294, DOI 10.1007/124_2018_17,
Published online: 28 February 2018
253