Biological Chemistry
Sanja Roje
One-Carbon Metabolism
and S-adenosylmethionine
Biosynthesis
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Methyl groups needed for nearly all methylation reactions in living organisms are donated by the universal donor S-adenosylmethionine, which is in turn synthesized from the amino acid methionine.
Methionine synthesis in plants proceeds in two branches. In the first branch, the non-protein amino acid homocysteine is synthesized from the amino acid aspartate. In the second branch, 5-methyltetrahydrofolate is synthesized from tetrahydrofolate and a one-carbon unit donor. The methyl group is then transferred from 5-methyltetrahydrofolate to homocysteine, yielding methionine. The second branch is also known as the one-carbon branch because it provides the methyl group required for methionine and
S-adenosylmethionine biosynthesis. Dr. Roje’s
research focuses on the second branch of methionine biosynthesis. She investigates enzymes
that catalyze formation of one-carbon tetra-hydrofolate derivatives, and enzymes that
reduce or oxidize the tetrahydrofolate-bound one-carbon groups in plants.
A recent focus of Dr. Roje’s research is the enzyme serine hydroxymethyltransferase. This enzyme catalyzes reversible formation of 5,10-methylenetetrahydrofolate and glycine from serine and tetrahydrofolate. In plant cells, this enzyme operates in mitochondria, chloroplasts, nuclei, and the cytosol. Plastidial and cytosolic serine hydroxymethyltransferases are thought to provide one-carbon units necessary for one-carbon metabolism in these subcellular compartments. Mitochondrial serine hydroxymethyltransferases are required for photorespiration. Dr. Roje’s NSF-funded research compares biochemical properties of serine hydroxymethyltransferases from mitochondria, plastids, and the cytosol. The roles of the nuclear serine hydroxymethyltransferases are currently a mystery. Dr. Roje has hypothesized that these enzymes participate in transcriptional regulation of one-carbon metabolism in plants. Her long-term goal is to test this hypothesis by biochemically characterizing the nuclear serine hydroxymethyltransferases, and by determining their physiological roles using reverse genetics.
Contact Information
Sanja Roje, Ph.D.
Assistant Professor
Institute of Biological Chemistry
Washington State University
P.O. Box 646340
Pullman, WA 99164-6340
Telephone: 509-335-3008
E-mail: sanja@wsu.edu
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