title: Expression, purification and enzymatic characterization of the catalytic domains of human tryptophan hydroxylase isoforms.
abstract: Tryptophan hydroxylase exists in two isoforms: Isoform 1 catalyses the first and rate-limiting step in the synthesis of serotonin in the peripheral parts of the body while isoform 2 catalyses this step in the brain. The catalytic domains of human tryptophan hydroxylase 1 and 2 have been expressed, purified and the kinetic properties have been studied and are compared. Substrate inhibition by tryptophan is observed for isoform 1 but not for isoform 2. Large differences are observed in the K (m,tetrahydrobiopterin) values for the two isoforms, being >10 times larger for isoform 1 compared to isoform 2.
authors.affiliation: Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Windahl
authors.forename: Jane
authors.initials: J
authors.lastname: Boesen
authors.forename: Pernille E
authors.initials: PE
authors.lastname: Karlsen
authors.forename: Hans E M
authors.initials: HE
authors.lastname: Christensen
mesh_terms: D020134:Catalytic Domain; D015870:Gene Expression; D006801:Humans; D007700:Kinetics; D020033:Protein Isoforms / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D014365:Tryptophan Hydroxylase / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; C497467:TPH1 protein, human; C494784:TPH2 protein, human; D014365:Tryptophan Hydroxylase