Differential tissue distribution of tryptophan hydroxylase isoforms 1 and 2 as revealed with monospecific antibodies

Brain Res. 2006 Apr 26;1085(1):11-8. doi: 10.1016/j.brainres.2006.02.047. Epub 2006 Apr 11.


Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the synthesis of the neurotransmitter serotonin. Once thought to be a single-gene product, TPH is now known to exist in two isoforms-TPH1 is found in the pineal and gut, and TPH2 is selectively expressed in brain. Heretofore, probes used for localization of TPH protein or mRNA could not distinguish between the TPH isoforms because of extensive homology shared by them at the nucleotide and amino acid level. We have produced monospecific polyclonal antibodies against TPH1 and TPH2 using peptide antigens from nonoverlapping sequences in the respective proteins. These antibodies allow the differentiation of TPH1 and TPH2 upon immunoblotting, immunoprecipitation, and immunocytochemical staining of tissue sections from brain and gut. TPH1 and TPH2 antibodies do not cross-react with either tyrosine hydroxylase or phenylalanine hydroxylase. Analysis of mouse tissues confirms that TPH1 is the predominant form expressed in pineal gland and in P815 mastocytoma cells with a molecular weight of 51 kDa. TPH2 is the predominant enzyme form expressed in brain extracts from mesencephalic tegmentum, striatum, and hippocampus with a molecular weight of 56 kDa. Antibody specificity against TPH1 and TPH2 is retained across mouse, rat, rabbit, primate, and human tissues. Antibodies that distinguish between the isoforms of TPH will allow studies of the differential regulation of their expression in brain and periphery.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antibodies / metabolism*
  • Antibody Formation
  • Brain / enzymology
  • Cell Line, Tumor
  • Duodenum / enzymology
  • Gene Expression Regulation, Enzymologic / physiology
  • Immunoblotting / methods
  • Immunohistochemistry / methods
  • Immunoprecipitation / methods
  • Isoenzymes / metabolism
  • Mastocytoma
  • Mice
  • Mice, Inbred C57BL
  • Molecular Weight
  • Recombinant Proteins / immunology
  • Tissue Distribution
  • Tryptophan Hydroxylase / immunology*
  • Tryptophan Hydroxylase / metabolism*


  • Antibodies
  • Isoenzymes
  • Recombinant Proteins
  • Tph1 protein, mouse
  • Tph2 protein, mouse
  • Tryptophan Hydroxylase