[Method for the direct spectrophotometric determination of the rate of the tyrosine hydroxylase reaction].
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).
D000042:Absorption; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007700:Kinetics; D010084:Oxidation-Reduction; D011622:Pterins / Q000378:metabolism; D013053:Spectrophotometry / Q000379:methods*; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis* / Q000378:metabolism
D011622:Pterins; D014446:Tyrosine 3-Monooxygenase
Metod priamogo spektrofotometricheskogo opredeleniia skorosti tirozingidroksilaznoĭ reaktsii