Plasma amine oxidase activities in Norrie disease patients with an X-chromosomal deletion affecting monoamine oxidase

J Neural Transm Gen Sect. 1991;83(1-2):1-12. doi: 10.1007/BF01244447.


Two individuals with an X-chromosomal deletion were recently found to lack the genes encoding monoamine oxidase type A (MAO-A) and MAO-B. This abnormality was associated with almost total (90%) reductions in the oxidatively deaminated urinary metabolites of the MAO-A substrate, norepinephrine, and with marked (100-fold) increases in an MAO-B substrate, phenylethylamine, confirming systemic functional consequences of the genetic enzyme deficiency. However, urinary concentrations of the deaminated metabolites of dopamine and serotonin (5-HT) were essentially normal. To investigate other deaminating systems besides MAO-A and MAO-B that might produce these metabolites of dopamine and 5-HT, we examined plasma amine oxidase (AO) activity in these two patients and two additional patients with the same X-chromosomal deletion. Normal plasma AO activity was found in all four Norrie disease-deletion patients, in four patients with classic Norrie disease without a chromosomal deletion, and in family members of patients from both groups. Marked plasma amine metabolite abnormalities and essentially absent platelet MAO-B activity were found in all four Norrie disease-deletion patients, but in none of the other subjects in the two comparison groups. These results indicate that plasma AO is encoded by gene(s) independent of those for MAO-A and MAO-B, and raise the possibility that plasma AO, and perhaps the closely related tissue AO, benzylamine oxidase, as well as other atypical AOs or MAOs encoded independently from MAO-A and MAO-B may contribute to the oxidative deamination of dopamine and 5-HT in humans.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Amine Oxidase (Copper-Containing)*
  • Blindness / enzymology
  • Blindness / genetics*
  • Chromosome Deletion
  • Dopamine / metabolism*
  • Female
  • Humans
  • Male
  • Monoamine Oxidase / deficiency*
  • Monoamine Oxidase / genetics
  • Norepinephrine / metabolism
  • Oxidoreductases Acting on CH-NH Group Donors / blood*
  • Phenethylamines / metabolism
  • Retina / abnormalities*
  • Serotonin / metabolism*
  • Sex Chromosome Aberrations / enzymology*
  • X Chromosome


  • Phenethylamines
  • Serotonin
  • Amine Oxidase (Copper-Containing)
  • Monoamine Oxidase
  • Oxidoreductases Acting on CH-NH Group Donors
  • Dopamine
  • Norepinephrine