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Simultaneous Measurement of Superoxide/Hydrogen Peroxide and NADH Production by Flavin-containing Mitochondrial Dehydrogenases
Published on: February 24, 2018
Comparative studies on nicotinamide nucleotide transhydrogenase from different sources.
J B Hoek1, J Rydström, B Höjeberg
1Biokemiska Institutionen, Kungl. Universitetet i Stockholm, Box 6409, S-113 82 Stockholm, Sweden.
Nicotinamide nucleotide transhydrogenases from E. coli, beef heart, and R. rubrum share similar properties, suggesting a link to energy-conserving membrane systems. However, P. aeruginosa transhydrogenase exhibits distinct characteristics, including allosteric regulation.
Area of Science:
- Biochemistry
- Enzymology
- Membrane Biology
Background:
- Nicotinamide nucleotide transhydrogenases (NNTs) are crucial enzymes involved in redox balance and energy metabolism.
- Understanding the variations in NNTs across different organisms is essential for elucidating their diverse biological roles.
Purpose of the Study:
- To compare the biochemical and regulatory properties of NNTs from diverse sources: beef heart mitochondria, Rhodospirillum rubrum chromatophores, Escherichia coli, and Pseudomonas aeruginosa.
- To investigate the stereospecificity, substrate reactivity, inhibition patterns, and allosteric regulation of these NNTs.
Main Methods:
- Comparative biochemical analysis of NNTs.
- Assays for stereospecificity (NADH 4-hydrogen), reactivity with 3'-NADP, inhibition by palmityl-CoA, and sensitivity to trypsin.
- Evaluation of the effects of Ca2+ and 2'-AMP on enzyme activity.
Main Results:
- NNTs from beef heart, R. rubrum, and E. coli exhibited A-side stereospecificity for NADH, were inhibited by palmityl-CoA, sensitive to trypsin, and did not react with 3'-NADP.
- These NNTs showed no significant response to Ca2+ or 2'-AMP.
- P. aeruginosa NNT displayed B-side stereospecificity for NADH, reacted with 3'-NADP, was insensitive to palmityl-CoA and trypsin, and was allosterically regulated by Ca2+ and 2'-AMP.
Conclusions:
- The conserved properties of NNTs in E. coli, R. rubrum, and beef heart suggest a functional association with energy-conserving membrane systems.
- The distinct characteristics of P. aeruginosa NNT indicate unique regulatory mechanisms and potential functional divergence.
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