module: dmel_tyramine_octopamine_biosynthesis
title: Tyramine and octopamine biosynthesis in Drosophila melanogaster
label: Tyramine and octopamine biosynthesis
module_type: METABOLIC_PATHWAY
description: >-
  Octopamine, the insect counterpart of noradrenaline, and its precursor
  tyramine are monoamine neurotransmitters and neurohormones. Tyrosine is
  decarboxylated to tyramine by tyrosine decarboxylase: Tdc2 in neurons and
  Tdc1 in non-neural tissues. Tyramine beta-hydroxylase (Tbh), a copper
  monooxygenase of the dopamine beta-hydroxylase family that acts inside
  secretory vesicles, then hydroxylates tyramine to octopamine. Loss of Tbh
  removes octopamine and causes female sterility from a failure of ovulation,
  and loss of Tdc2 removes both amines from the nervous system.
summary: >-
  Two-step synthesis of tyramine by tyrosine decarboxylase and of octopamine by
  tyramine beta-hydroxylase.
concepts:
  - {id: GO:0006589, label: octopamine biosynthetic process}
  - {id: GO:1901695, label: tyramine biosynthetic process}
parts:
  - id: tyrosine_decarboxylation
    label: Tyrosine decarboxylation
    role: step 1, tyrosine to tyramine
    module_type: REACTION
    genes: [Tdc1, Tdc2]
    function: {id: GO:0004837, label: tyrosine decarboxylase activity}
    roles:
      Tdc1: non-neural tyrosine decarboxylase
      Tdc2: neural tyrosine decarboxylase
  - id: tyramine_hydroxylation
    label: Tyramine beta-hydroxylation
    role: step 2, tyramine to octopamine
    module_type: REACTION
    genes: [Tbh, olf413]
    function: {id: GO:0004836, label: tyramine-beta hydroxylase activity}
    unit_functions:
      olf413: null
connections:
  - source: tyrosine_decarboxylation
    target: tyramine_hydroxylation
    connection_type: PRECEDES
    description: Tyramine is hydroxylated to octopamine.
notes: >-
  Tdc1 and Tdc2 are alternative enzymes for the same step with different tissue
  distribution, and each is a separate annoton. olf413 is a second
  dopamine-beta-hydroxylase-like monooxygenase that FlyBase places in this
  group; it has been proposed to contribute to octopamine synthesis, but its
  activity has not been measured, so it has no molecular function here.
  Tyramine is a signalling molecule in its own right, so the decarboxylation
  step is also the end of tyramine synthesis. Vesicular uptake, release and
  receptors are outside the module.