Catecholamine synthesis is mediated by tyrosinase in the absence of tyrosine hydroxylase

Maribel Rios, Beth Habecker, Toshikuni Sasaoka, Graeme Eisenhofer, Hua Tian, Story Landis, Dona Chikaraishi, Suzanne Roffler-Tarlov

Research output: Contribution to journalArticlepeer-review

113 Scopus citations


Catecholamine neurotransmitters are synthesized by hydroxylation of tyrosine to L-dihydroxyphenylalanine (L-Dopa) by tyrosine hydroxylase (TH). The elimination of TH in both pigmented and albino mice described here, like pigmented TH-null mice reported previously (Kobayashi et al., 1995; Zhou et al., 1995), demonstrates the unequivocal requirement for catecholamines during embryonic development. Although the lack of TH is fatal, TH-null embryos can be rescued by administration of catecholamine precursors to pregnant dams. Once born, TH-null pups can survive without further treatment until weaning. Given the relatively rapid half-life of catecholamines, we expected to find none in postnatal TH-null pups. Despite the fact that the TH-null pups lack TH and have not been supplemented with catecholamine precursers, catecholamines are readily detected in our pigmented line of TH- null mice by glyoxylic acid-induced histofluorescence at postnatal day 7 (P7) and P15 and quantitatively at P15 in sympathetically innervated peripheral organs, in sympathetic ganglia, in adrenal glands, and in brains. Between 2 and 22% of wild-type catecholamine concentrations are found in these tissues n mutant pigmented mice. To ascertain the source of the catecholamine, we examined postnatal TH-null albino mice that lack tyrosinase, another enzyme that converts tyrosine to L-DOpa but does so during melanin synthesis. In contrast to the pigmented TH-null mice, catecholamine histofluorescence is undetectable in postnatal albino mutants, and the catecholamine content of TH-null pups lacking tyrosinase is 18% or less than that of TH-null mice with tyrosinase. Thus, these extraordinary circumstances reveal that tyrosinase serves as an alternative pathway to supply catecholamines.

Original languageEnglish (US)
Pages (from-to)3519-3526
Number of pages8
JournalJournal of Neuroscience
Issue number9
StatePublished - May 1 1999
Externally publishedYes


  • Catecholamine synthesis
  • Catecholamines
  • Catecholamines in development
  • Tyrosinase
  • Tyrosinase and catecholamine synthesis
  • Tyrosine hydroxylase
  • Tyrosine hydroxylase-null mutation

ASJC Scopus subject areas

  • Neuroscience(all)


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