VOPROSY MEDITSINSKOI KHIMII (ISSN 0042-8809)

Method for the direct spectrophotometric determination of the rate of the tyrosine hydroxylase reaction

   
Mineeva-Vialykh M.F.
PubMed Id: 16396
Year: 1976  Volume: 22  Issue: 2  Pages: 274-279
A rate of the tyrosine hydroxylase reaction was estimated by an increase in absorption at 335 nm, which was caused by oxidation of pterin cofactor 6,7-dimethyl-5, 6, 7, 8-tetrahydroxypterin (DMPH) coupled with the convertion of the substrate 1-tyrosine into dihydroxyphenylalanine. At pH 6.2 the ratios of molar extinction were as follows: in trisacetate ADMPH4-1370, ADMPH2-5350; in tris-malate tadmph4-1250, admph25300. the enzyme, associated with membranes, had the Km value for Tyr-0.045 mM, the Km for DMPH4 was 0.18 mM; the soluble enzyme had Km for Tyr-0,050 mM, the Km for DMPH4 was 0.74 mM. The stoichiometry of the reaction was 1:1 (I mole DOPA per I mole of DMPH2 formed).
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Mineeva-Vialykh M.F. (1976) Voprosy meditsinskoi khimii, 22(2), 274-279.
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