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PubMed · 6264261

The melatonin rhythm generating system: developmental aspects.

D C Klein·M A Namboodiri·D A Auerbach
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Acetylserotonin O-MethyltransferaseAnimalsAromatic-L-Amino-Acid DecarboxylasesArylamine N-AcetyltransferaseCircadian RhythmCyclic AMPFemaleGestational AgeHypothalamusMaternal-Fetal ExchangeMelatoninMonoamine OxidasePineal GlandPregnancyRatsReceptors, Adrenergic, betaRetinaSerotoninSupraoptic NucleusTryptophanJournal ArticleReview

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D C Klein, M A Namboodiri, D A Auerbach. 1981-05-04. The melatonin rhythm generating system: developmental aspects.. https://doi.org/10.1016/0024-3205(81)90644-5

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PubMed1992

Molecular cloning and nucleotide sequence of a cDNA encoding hydroxyindole O-methyltransferase from chicken pineal gland.

Hydroxyindole O-methyltransferase (EC 2.1.1.4) is the enzyme that catalyses the synthesis of melatonin in the pineal gland and in the retina. Polyadenylated RNA from chicken pineal glands was used to prepare a cDNA library in lambda gt11. The library was screened with an antiserum directed against chicken hydroxyindole O-methyltransferase, and one cDNA clone was isolated. The fusion protein expressed by phage lysogens was identified on Western blots as a 165 kDA immunoreactive protein (beta-galactosidase, 110 kDa; hydroxyindole O-methyltransferase, 38 kDa). The fusion protein exhibited hydroxyindole O-methyltransferase activity. Its Km values for N-acetyl-5-hydroxytryptamine and S-adenosylmethionine were 5 times those of the natural enzyme. The intrinsic activity of the fusion protein was approx. 0.25% that of the natural enzyme. The cDNA consisted of 1436 nucleotides, including a 1038-nucleotide sequence encoding a full-length 346-amino-acid hydroxyindole O-methyltransferase. Comparison with bovine hydroxyindole O-methyltransferase [Ishida, Obinata & Deguchi (1987) J. Biol. Chem. 262, 2895-2899] revealed 52% identity in nucleotide sequences and 44% identity in peptide sequences. Northern-blot analysis revealed the presence of hydroxyindole O-methyltransferase mRNA transcripts in chicken pineal gland and retina, but not in the telencephalon.

Acetylserotonin O-Methyltransferase↗
PubMed1992

Long-term effects of constant light or darkness on chicken pineal hydroxyindole-O-methyltransferase expression: biochemical and cellular aspects.

1. Chickens kept in constant light, as opposed to constant darkness, display a twofold increase in the activity of pineal hydroxyindole-O-methyltransferase (HIOMT), the last acting enzyme in the melatonin pathway. 2. Using an immunological approach, we presently show that this regulation of HIOMT activity reflects changes in the concentration of a single molecular form of the enzyme protein (a 38 kDa polypeptide). Immunohistofluorescence indicates that these concentration changes concurrently affect modified photoreceptors and pinealocyte-like cells in the chicken pineal organ. 3. Together, the present data support the hypothesis that environmental lighting might regulate the expression of the HIOMT gene.

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