Aquifex aeolicus VF5 Pathway: glycine biosynthesis I
Inferred by computational analysis

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: BiosynthesisAmino Acids BiosynthesisProteinogenic Amino Acids BiosynthesisGlycine 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

This organism is in the expected taxonomic range for this pathway.

Key to pathway glyph edge colors:

  An enzyme catalyzing this reaction is present in this organism
  The reaction is unique to this pathway in MetaCyc

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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