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Gazaryan IG, Shchedrina VA, Klyachko NL, Zakhariants AA, Kazakov SV, Brown AM. Zinc Switch in Pig Heart Lipoamide Dehydrogenase: Steady-State and Transient Kinetic Studies of the Diaphorase Reaction. Biochemistry (Mosc) 2020; 85:908-919. [PMID: 33045951 DOI: 10.1134/s0006297920080064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Elevation of intracellular Zn2+ following ischemia contributes to cell death by affecting mitochondrial function. Zn2+ is a differential regulator of the mitochondrial enzyme lipoamide dehydrogenase (LADH) at physiological concentrations (Ka = 0.1 µM free zinc), inhibiting lipoamide and accelerating NADH dehydrogenase activities. These differential effects have been attributed to coordination of Zn2+ by LADH active-site cysteines. A detailed kinetic mechanism has now been developed for the diaphorase (NADH-dehydrogenase) reaction catalyzed by pig heart LADH using 2,6-dichlorophenol-indophenol (DCPIP) as a model quinone electron acceptor. Anaerobic stopped-flow experiments show that two-electron reduced LADH is 15-25-fold less active towards DCPIP reduction than four-electron reduced enzyme, or Zn2+-modified reduced LADH (the corresponding values of the rate constants are (6.5 ± 1.5) × 103 M-1·s-1, (9 ± 2) × 104 M-1·s-1, and (1.6 ± 0.5) × 105 M-1·s-1, respectively). Steady-state kinetic studies with different diaphorase substrates show that Zn2+ accelerates reaction rates exclusively for two-electron acceptors (duroquinone, DCPIP), but not for one-electron acceptors (benzoquinone, ubiquinone, ferricyanide). This implies that the two-electron reduced form of LADH, prevalent at low NADH levels, is a poor two-electron donor compared to the four-electron reduced or Zn2+-modified reduced LADH forms. These data suggest that zinc binding to the active-site thiols switches the enzyme from one- to two-electron donor mode. This zinc-activated switch has the potential to alter the ratio of superoxide and H2O2 generated by the LADH oxidase activity.
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Affiliation(s)
- I G Gazaryan
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10605, USA.,Department of Chemistry and Physical Sciences, Dyson College of Arts and Sciences, Pace University, Pleasantville, NY 10570, USA.,Department of Chemical Enzymology, Lomonosov Moscow State University, Moscow, 119899, Russia.,Bach Institute of Biochemistry, Federal Research Centre "Fundamentals of Biotechnology", Russian Academy of Sciences, Moscow, 119071, Russia
| | - V A Shchedrina
- Department of Chemical Enzymology, Lomonosov Moscow State University, Moscow, 119899, Russia
| | - N L Klyachko
- Department of Chemical Enzymology, Lomonosov Moscow State University, Moscow, 119899, Russia.,Derzhavin Tambov State University, Tambov, 392000, Russia
| | - A A Zakhariants
- Bach Institute of Biochemistry, Federal Research Centre "Fundamentals of Biotechnology", Russian Academy of Sciences, Moscow, 119071, Russia.,Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
| | - S V Kazakov
- Department of Chemistry and Physical Sciences, Dyson College of Arts and Sciences, Pace University, Pleasantville, NY 10570, USA
| | - A M Brown
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10605, USA.
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Smirnova NA, Osipyants AI, Khristichenko AY, Hushpulian DM, Nikulin SV, Chubar TA, Zakhariants AA, Tishkov VI, Gazaryan IG, Poloznikov AA. HIF2 ODD-luciferase reporter: the most sensitive assay for HIF prolyl hydroxylase inhibitors. Russ Chem Bull 2018. [DOI: 10.1007/s11172-018-2051-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Osipyants AI, Smirnova NA, Khristichenko AY, Hushpulian DM, Nikulin SV, Chubar TA, Zakhariants AA, Tishkov VI, Gazaryan IG, Poloznikov AA. Enzyme–substrate reporters for evaluation of substrate specificity of HIF prolyl hydroxylase isoforms. Biochemistry Moscow 2017; 82:1207-1214. [DOI: 10.1134/s0006297917100145] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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