Aquifex aeolicus VF5 Pathway: glycine biosynthesis I

Pathway diagram: glycine biosynthesis I

If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Locations of Mapped Genes:

Schematic showing all replicons, marked with selected genes

Superclasses: Biosynthesis Amino Acids Biosynthesis Proteinogenic Amino Acids Biosynthesis Glycine Biosynthesis

Pathway Summary from MetaCyc:
General Background

Saccharomyces cerevisiae can biosynthesize glycine via three different pathways.

When the cells are grown with glucose as the carbon source, two alternative pathways operate. In one pathway L-threonine aldolase, encoded by GLY1, produces glycine from L-threonine (which is produced from the glycolytic intermediate oxaloacetate) (see glycine biosynthesis IV). In the other pathway glycine is formed from L-serine (a product of 3-phospho-D-glycerate, another glycolytic intermediate) via two serine hydroxymethyltransferases - a cytosolic enzyme (SHMT2) and a mitochondrial enzyme (SHMT1) (see glycine biosynthesis I). The two isoforms are reported to work in opposite directions, depending on the culture conditions [Kastanos97].

When the cells are grown with a non-fermentable carbon source, such as ethanol and acetate, glycine is produced from glyoxylate, a product of the glyoxylate cycle, by the enzyme alanine--glyoxylate aminotransferase 1 (see glycine biosynthesis III).

About This Pathway

This single reaction pathway, catalyzed by serine hydroxymethyltransferase, is the major pathway for biosynthesis of glycine in Escherichia coli K-12, and the main source for one carbon units, which are stored in the form of 5,10-methylenetetrahydropteroyl mono-L-glutamate.

In Saccharomyces cerevisiae, mitochondrial and cytoplasmic serine hydroxymethyltransferase (SHMT) isozymes are encoded by distinct nuclear genes (SHM1 and SHM2). As in Escherichia coli, SHMT is the major provider of not only glycine, but also of one-carbon units [Kastanos97].

When yeast was grown on L-serine as the primary one-carbon source, the cytoplasmic isozyme was the main provider of glycine and one-carbon groups for purine synthesis. When grown on glycine, the mitochondrial SHMT was the predominant isozyme catalyzing the synthesis of serine from glycine and one-carbon units. However, when both serine and glycine were present, the mitochondrial SHMT made a significant contribution of one-carbon units, but not glycine, for purine synthesis [Kastanos97].

Superpathways: superpathway of serine and glycine biosynthesis I

Variants: glycine biosynthesis II

Pathway Evidence Glyph:

Pathway evidence glyph

Key to pathway glyph edge colors: ?

  An enzyme catalyzing this reaction is present in this organism
  The reaction and any enzyme that catalyzes it (if one has been identified) is unique to this pathway

Created in MetaCyc 08-Jul-1994 by Riley M , Marine Biological Laboratory
Revised in MetaCyc 07-Jan-2008 by Caspi R , SRI International
Imported from MetaCyc 08-Aug-2014 by Subhraveti P , SRI International


Kastanos97: Kastanos EK, Woldman YY, Appling DR (1997). "Role of mitochondrial and cytoplasmic serine hydroxymethyltransferase isozymes in de novo purine synthesis in Saccharomyces cerevisiae." Biochemistry 36(48);14956-64. PMID: 9398220

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Hanson02: Hanson AD, Gregory JF (2002). "Synthesis and turnover of folates in plants." Curr Opin Plant Biol 5(3);244-9. PMID: 11960743

Jabrin03: Jabrin S, Ravanel S, Gambonnet B, Douce R, Rebeille F (2003). "One-carbon metabolism in plants. Regulation of tetrahydrofolate synthesis during germination and seedling development." Plant Physiol 131(3);1431-9. PMID: 12644692

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Lucock00: Lucock M (2000). "Folic acid: nutritional biochemistry, molecular biology, and role in disease processes." Mol Genet Metab 71(1-2);121-38. PMID: 11001804

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Page generated by SRI International Pathway Tools version 19.0 on Wed Apr 1, 2015, biocyc13.