Sulfur and Cysteine Metabolism
- Rainer Hoefgen and
- Holger Hesse
The influence of the plant macronutrient sulfur on plant metabolism and on crop productivity has long been underestimated. Sulfur enters cellular metabolism usually as sulfate ion, and a suite of sulfate transporters is responsible for its uptake via roots and for its distribution within the plant or between subcellular compartments. The inert sulfate ion needs to be activated by binding to ATP to be assimilated and to enter cellular metabolism, essentially being subject to two fates then, both essential for plant life. First, the ATP-bound sulfate is used for sulfatation reactions of biomolecules without further reduction steps. Second, sulfate is reduced in a series of reduction steps to sulfide, which is then fixed into the proteinogenic thiol amino acid cysteine. Cysteine is the common precursor of all organic molecules containing a reduced sulfur moiety such as glutathione, which is involved in redox control and stress response, the essential amino acid methionine, the versatile one-carbon donor S-adenosylmethionine, hormones, vitamins, and cofactors such as acetyl-CoA. Uptake and assimilation of sulfate and its integration with other plant metabolic pathways such as nitrogen and carbon levels is tightly regulated through control of gene expression or enzyme activity. The most important control points are the reduction step to sulfite by the enzyme APS reductase and the cysteine synthase complex, which uses interaction of the enzymes serine acetyltransferase and O-acetylserine-(thiol)-lyase to control flux through the pathway.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2008. American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, 5585 Guilford Road, Madison, WI 53711-5801, USA. Sulfur: A Missing Link between Soils, Crops, and Nutrition. Agronomy Monograph 50.