Rostrup M 2008 Amino Acids

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Rostrup M, Fossbakk A, Hauge A, Kleppe R, Gnaiger E, Haavik J (2008) Oxygen dependence of tyrosine hydroxylase. Amino Acids 34:455-64.

» 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: MiParea: Instruments;methods 


Organism: Human 

Preparation: Enzyme, Oxidase;biochemical oxidation 

Regulation: Oxygen kinetics, Substrate 

Pathway: ROX  HRR: Oxygraph-2k