Rostrup M 2008 Amino Acids: Difference between revisions
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|abstract=The effects of dioxygen on tyrosine hydroxylase (TH) activity was studied, measuring the formation of DOPA from tyrosine, 3H<sub>2</sub>O from 3,5-3H-tyrosine, or by direct oxygraphic determination of oxygen consumption. A high enzyme activity was observed during the initial 1โ2 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 29โ45 ยตM for dioxygen were determined for all human TH isoforms, i.e. 2โ40 times higher than previously reported for TH isolated from animal tissues. After 8 min incubation, the Km (O<sub>2</sub>)-values had declined to an average of 20 ยฑ 4 ยตM. 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. | |abstract=The effects of dioxygen on tyrosine hydroxylase (TH) activity was studied, measuring the formation of DOPA from tyrosine, 3H<sub>2</sub>O from 3,5-3H-tyrosine, or by direct oxygraphic determination of oxygen consumption. A high enzyme activity was observed during the initial 1โ2 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 29โ45 ยตM for dioxygen were determined for all human TH isoforms, i.e. 2โ40 times higher than previously reported for TH isolated from animal tissues. After 8 min incubation, the Km (O<sub>2</sub>)-values had declined to an average of 20 ยฑ 4 ยตM. 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 | |keywords=Catecholamines, Human, Hypoxia, Oxygen, Tyrosine hydroxylase | ||
|mipnetlab=AT_Innsbruck_Gnaiger E | |mipnetlab=AT_Innsbruck_Gnaiger E, AT Innsbruck MitoCom | ||
|discipline=Biomedicine | |discipline=Biomedicine | ||
}} | }} |
Revision as of 15:11, 6 December 2012
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 1โ2 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 29โ45 ยตM for dioxygen were determined for all human TH isoforms, i.e. 2โ40 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 ยฑ 4 ยตM. 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. โข Keywords: Catecholamines, Human, Hypoxia, Oxygen, Tyrosine hydroxylase
โข O2k-Network Lab: AT_Innsbruck_Gnaiger E, AT Innsbruck MitoCom
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