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. |
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 1β2 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 29β45 Β΅M for dioxygen were determined for all human TH isoforms, i.e. 2β40 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 Β± 4 Β΅M. 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. β’ Keywords: Catecholamines, Human, Hypoxia, Oxygen, Tyrosine hydroxylase
β’ O2k-Network Lab: AT_Innsbruck_Gnaiger E
Labels:
Stress:Hypoxia Organism: Human
Preparation: Enzyme
HRR: Oxygraph-2k