module: dmel_trehalose_metabolism
title: Trehalose synthesis, transport and breakdown in Drosophila melanogaster
label: Trehalose metabolism
module_type: METABOLIC_PATHWAY
description: >-
  Trehalose, a glucose disaccharide, is the main circulating sugar in insect
  hemolymph. In the fat body, trehalose-6-phosphate synthase 1 (Tps1), a
  bifunctional enzyme with synthase and phosphatase domains, makes trehalose
  from UDP-glucose and glucose-6-phosphate. Trehalose leaves the fat body and
  enters target cells through the facilitative transporter Tret1, and in target
  tissues trehalase (Treh) hydrolyses it into two glucose molecules for
  glycolysis and other uses. Trehalose levels buffer hemolymph sugar and protect
  against stress.
summary: >-
  Fat-body synthesis of trehalose by Tps1, its transport by Tret1 and its
  hydrolysis to glucose by trehalase.
concepts:
  - {id: GO:0005992, label: trehalose biosynthetic process}
  - {id: GO:0005993, label: trehalose catabolic process}
parts:
  - id: trehalose_synthesis
    label: Trehalose synthesis
    role: step 1, UDP-glucose and glucose-6-phosphate to trehalose
    module_type: REACTION
    genes: [Tps1]
    function: {id: GO:0003825, label: "alpha,alpha-trehalose-phosphate synthase (UDP-forming) activity"}
    processes:
      - {id: GO:0005992, label: trehalose biosynthetic process}
  - id: trehalose_transport
    label: Trehalose transport
    role: step 2, transmembrane transport of trehalose
    module_type: TRANSPORT_STEP
    genes: [Tret1]
    function: {id: GO:0015574, label: trehalose transmembrane transporter activity}
  - id: trehalose_hydrolysis
    label: Trehalose hydrolysis
    role: step 3, trehalose to two glucose
    module_type: REACTION
    genes: [Treh]
    function: {id: GO:0004555, label: "alpha,alpha-trehalase activity"}
    processes:
      - {id: GO:0005993, label: trehalose catabolic process}
connections:
  - source: trehalose_synthesis
    target: trehalose_transport
    connection_type: PRECEDES
    description: Trehalose made in the fat body is exported to the hemolymph.
  - source: trehalose_transport
    target: trehalose_hydrolysis
    connection_type: PRECEDES
    description: Trehalose taken up or present in tissues is hydrolysed by trehalase.
notes: >-
  Tps1 carries both the trehalose-6-phosphate synthase and the
  trehalose-6-phosphate phosphatase activities (flies have no separate
  phosphatase gene in the group); the annoton gives the synthase activity, which
  defines the committed step. Tret1 is in both FlyBase groups (biosynthesis and
  catabolism) and appears once, between the two enzymes. Treh encodes both
  secreted and intracellular trehalase isoforms. Glycogen and glucose
  metabolism, which supply and consume the substrates, are outside the module.