From sulfur to homoglutathione: thiol metabolism in soybean

Abstract

Sulfur is an essential plant nutrient and is metabolized into the sulfur-containing amino acids (cysteine and methionine) and into molecules that protect plants against oxidative and environmental stresses. Although studies of thiol metabolism in the model plant Arabidopsis thaliana (thale cress) have expanded our understanding of these dynamic processes, our knowledge of how sulfur is assimilated and metabolized in crop plants, such as soybean (Glycine max), remains limited in comparison. Soybean is a major crop used worldwide for food and animal feed. Although soybeans are protein-rich, they do not contain high levels of the sulfur-containing amino acids, cysteine and methionine. Ultimately, unraveling the fundamental steps and regulation of thiol metabolism in soybean is important for optimizing crop yield and quality. Here we review the pathways from sulfur uptake to glutathione and homoglutathione synthesis in soybean, the potential biotechnology benefits of understanding and modifying these pathways, and how information from the soybean genome may guide the next steps in exploring this biochemical system.

Nucleotide Binding Site Communication in Arabidopsis thaliana Adenosine 5′-Phosphosulfate Kinase

“…5), which provides a driving force for nucleotide recognition as it forms nine hydrogen bonds with the ␤-phosphate compared with two hydrogen bonds made between the rest of the nucleotide and protein (23)(24)(25)(26)(27)(28)(29)(30). Comparable interactions are observed for SO 4 2Ϫ bound in the AtAPSK⅐APS⅐SO 4 2Ϫ complex (Fig. 5).…”

“…Clear electron density for bound APS was observed in the active site with additional discontinuous density near the P-loop of the ATP/ADP binding site (Fig. 5A), which was modeled as SO 4 2Ϫ . Multiple interactions were formed between the SO 4 2Ϫ and residues in the P-loop (Fig.…”

“…lation of APS into PAPS, which is used for sulfur assimilation and as a biosynthetic sulfate donor (1)(2)(3)(4)(5). In plants, the sulfur assimilatory pathway branches after formation of APS into primary and secondary pathways.…”

“…The reductive (i.e. primary) route leads to the production of sulfur-containing amino acids and peptides (2)(3)(4)(5)(6). The second metabolic route begins with APS kinase and synthesizes PAPS as a sulfate donor for the sulfonation of brassinosteroids, peptide hormones, and molecules critical for protection against herbivores, such as glucosinolates (8 -10).…”

Structure and Mechanism of Soybean ATP Sulfurylase and the Committed Step in Plant Sulfur Assimilation

“…In plants, the uptake of sulfate and its assimilation provide an essential nutrient for the synthesis of a diverse set of metabolites, including cysteine, methionine, glutathione, iron-sulfur clusters, vitamin cofactors like biotin and thiamin, and multiple specialized metabolites such as glucosinolates (1)(2)(3)(4)(5)(6)(7)(8). The central role of sulfur metabolism in plants and its integration with carbon and nitrogen metabolism and the biosynthesis of multiple specialized metabolites have led to efforts to understand this critical pathway for applications in nutritional enhancement for food and feed and for improved plant growth under environmental stresses (2, 9 -15).…”