Rostrup M 2008 Amino Acids

Rostrup M, Fossbakk A, Hauge A, Kleppe R, Gnaiger E, Haavik J (2008) Oxygen dependence of tyrosine hydroxylase. Amino Acids 34: 455-464.

» PMID: 17520326

Rostrup M, Fossbakk A, Hauge A, Kleppe R, Gnaiger E, Haavik J (2008) Amino Acids

Abstract: The effects of dioxygen on tyrosine hydroxylase (TH) activity was studied, measuring the formation of DOPA from tyrosine, 3H₂O from 3,5-3H-tyrosine, or by direct oxygraphic determination of oxygen consumption. A high enzyme activity was observed during the initial 1–2 min of the reactions, followed by a decline in activity, possibly related to a turnover dependent substoichiometrical oxidation of enzyme bound Fe(II) to the inactive Fe(III) state. During the initial reaction phase, apparent Km-values of 29–45 µM for dioxygen were determined for all human TH isoforms, i.e. 2–40 times higher than previously reported for TH isolated from animal tissues. After 8 min incubation, the Km (O₂)-values had declined to an average of 20 ± 4 µM. Thus, TH activity may be severely limited by oxygen availability even atmoderate hypoxic conditions, and the enzyme is rapidly and turnover dependent inactivated at the experimental conditions commonly employed to measure in vitro activities. • Keywords: Catecholamines, Human, Hypoxia, Oxygen, Tyrosine hydroxylase

• O2k-Network Lab: AT_Innsbruck_Gnaiger E

Labels:

Stress:Hypoxia  Organism: Human 

Preparation: Oxidase; Biochemical Oxidation"Oxidase; Biochemical Oxidation" is not in the list (Intact organism, Intact organ, Permeabilized cells, Permeabilized tissue, Homogenate, Isolated mitochondria, SMP, Chloroplasts, Enzyme, Oxidase;biochemical oxidation, ...) of allowed values for the "Preparation" property., Enzyme 

HRR: Oxygraph-2k