module: dmel_arginine_metabolism
title: L-arginine metabolism in Drosophila melanogaster
label: L-arginine metabolism
module_type: METABOLIC_PATHWAY
description: >-
  Three conserved urea-cycle enzymes interconvert citrulline, arginine and
  ornithine in Drosophila. Argininosuccinate synthase (Ass) condenses
  citrulline with aspartate to form argininosuccinate, argininosuccinate lyase
  (Argl) cleaves it to arginine and fumarate, and arginase (Arg) hydrolyses
  arginine to ornithine and urea. Together the first two steps regenerate
  arginine from citrulline, and arginase links arginine to ornithine, the
  precursor of proline and polyamines. Insects are not known to run a complete
  urea cycle, so the three enzymes act as a branch of amino acid metabolism
  rather than as the main route of nitrogen excretion.
summary: >-
  Ass and Argl regenerate arginine from citrulline, and arginase converts
  arginine to ornithine and urea.
concepts:
  - {id: GO:0006525, label: arginine metabolic process}
parts:
  - id: argininosuccinate_synthesis
    label: Argininosuccinate synthesis
    role: citrulline + aspartate to argininosuccinate
    genes: [Ass]
    function: {id: GO:0004055, label: argininosuccinate synthase activity}
  - id: argininosuccinate_cleavage
    label: Argininosuccinate cleavage
    role: argininosuccinate to arginine + fumarate
    genes: [Argl]
    function: {id: GO:0004056, label: argininosuccinate lyase activity}
  - id: arginine_hydrolysis
    label: Arginine hydrolysis
    role: arginine to ornithine + urea
    genes: [Arg]
    function: {id: GO:0004053, label: arginase activity}
connections:
  - source: argininosuccinate_synthesis
    target: argininosuccinate_cleavage
    connection_type: PRECEDES
    description: Argininosuccinate made by Ass is the substrate of Argl.
  - source: argininosuccinate_cleavage
    target: arginine_hydrolysis
    connection_type: PRECEDES
    description: Arginine released by Argl can be hydrolysed by arginase.
notes: >-
  Boundary. The module covers the three FlyBase L-arginine metabolism enzymes.
  Arginine use by nitric oxide synthase (which yields citrulline) and by
  arginine kinase, and ornithine use for proline and polyamine synthesis, are
  connected pathways and not parts. The enzyme functions are assigned by
  orthology to the well-characterized urea-cycle enzymes.
group: ARGMET