module: dmel_glycine_biosynthesis
title: Glycine biosynthesis in Drosophila melanogaster
label: Glycine biosynthesis
module_type: METABOLIC_PATHWAY
description: >-
  Glycine can be made by two routes. From threonine, mitochondrial L-threonine
  3-dehydrogenase (Tdh) oxidizes threonine to 2-amino-3-ketobutyrate, which
  2-amino-3-ketobutyrate CoA ligase (Gcat) cleaves with coenzyme A into glycine
  and acetyl-CoA. From serine, serine hydroxymethyltransferase (Shmt) converts
  serine and tetrahydrofolate to glycine and 5,10-methylenetetrahydrofolate,
  linking glycine supply to one-carbon metabolism. Both reactions are
  reversible or bidirectional in context, so the enzymes also contribute to
  glycine and serine interconversion.
summary: >-
  Glycine production from threonine (Tdh then Gcat) and from serine (Shmt).
concepts:
  - {id: GO:0006545, label: glycine biosynthetic process}
parts:
  - id: threonine_dehydrogenation
    label: Threonine dehydrogenation
    role: threonine to 2-amino-3-ketobutyrate
    genes: [Tdh]
    function: {id: GO:0008743, label: L-threonine 3-dehydrogenase activity}
  - id: aminoketobutyrate_cleavage
    label: 2-amino-3-ketobutyrate cleavage
    role: 2-amino-3-ketobutyrate + CoA to glycine + acetyl-CoA
    genes: [Gcat]
    function: {id: GO:0008890, label: glycine C-acetyltransferase activity}
  - id: serine_to_glycine
    label: Serine to glycine conversion
    role: serine + tetrahydrofolate to glycine
    genes: [Shmt]
    function: {id: GO:0004372, label: glycine hydroxymethyltransferase activity}
connections:
  - source: threonine_dehydrogenation
    target: aminoketobutyrate_cleavage
    connection_type: PRECEDES
    description: 2-amino-3-ketobutyrate formed by Tdh is cleaved by Gcat.
notes: >-
  Boundary. The threonine route (Tdh, Gcat) and the serine route (Shmt) are
  alternative sources of glycine and are not connected to each other. Shmt is
  also listed in the L-carnitine biosynthesis module as a candidate
  hydroxytrimethyllysine aldolase. Enzyme functions are assigned by orthology.
group: GLYBITH