Atypical profiles and modulations of heme-enzymes catalyzed outcomes by low amounts of diverse additives suggest diffusible radicals' obligatory involvement in such redox reactions

Manoj, Kelath Murali; Parashar, Abhinav; Venkatachalam, Avanthika; Goyal, Sahil; Satyalipsu,; Singh, Preeti Gunjan; Gade, Sudeep Kumar; Periyasami, Kalaiselvi; Jacob, Reeba S.; Sardar, Debosmita; Singh, Shubham; Kumar, Rajan; Gideon, Daniel Andrew

doi:10.1016/j.biochi.2016.03.003

Cited by 58 publications

(98 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…14 Further, binding of small species to membranebound proteins with deep-seated active sites would be relatively slow, owing to constraints imposed by diffusion. 13 Such a reality translates to the conservative requirement of g/Kg or g/L dosage administration for achieving Cox hemeFe binding-based lethal effects (confirming the calculations in point B above). Thus, binding-based calculations fall short of explaining the theoretically required dosage outcomes by several orders of magnitude.…”

Section: Cn Binding In Physiological Regimesmentioning

confidence: 55%

“…Even in such conditions, binding is via a non-covalent and coordination scheme of 'off-now, on-now' kind of interaction, and it is not an 'always bound' scenario. 11 As measured by non-invasive spectroscopic assays in pure solutions, cyanide binding to micromolar levels of hemeproteins show K d values ~10 -3 M. [12][13][14] In particular, the affinitybased K d of cyanide for Cox approaches the mM ranges (quite similar to that of oxygen) and cyanide has relatively low affinities for the oxidized form of Cox. 14 Further, binding of small species to membranebound proteins with deep-seated active sites would be relatively slow, owing to constraints imposed by diffusion.…”

Section: Cn Binding In Physiological Regimesmentioning

confidence: 99%

“…In the various hemeperoxiases and mixed oxidase cytochrome P450 systems, similar prevailing fallacies were pointed out and the kinetic/mechanistic phenomena were explained with murburn concept. 3,4,12,13,20,21…”

Section: Comparison Of Equilibrium and Kinetic Constants Of Cn With Omentioning

confidence: 99%

“…12,13,[31][32][33] This implies that only at higher heme:ligand ratios and high enzyme concentrations, an ion like cyanide serves as an efficient active-site ligand. The in situ or in vitro assays show a low functional IC 50 or pseudo-K i or pseudo-K M (~10 -6 M) for certain enzyme reactions, 12,13,[31][32][33] which cannot be explained by binding-based effects and which captures the essence of physiological toxicities. We have also provided several evidence based arguments that DROS generated in milieu are obligatorily involved and utilized in several heme-enzyme catalyzed specific/selective reactions.…”

Section: Explaining the Reaction Chemistry At Complex IV And The Effementioning

confidence: 99%

“…It was recently proposed that DROS are ultimately and obligatorily required as catalytic agents for metabolic activities and electron transfer (not just as molecular messengers); particularly for ATP-synthesis and heat generation in mitochondria. [3][4][5][6][7]13,32,33 Now, the thought lines that the toxicity difference must primarily lie in the reaction/interaction dynamics with DROS makes better rationale, particularly under the light of the structure-function correlations of mitochondrial proteins. For, the mitochondrial respiratory proteins (Complexes I through IV) show ADP binding sites, O 2 accessible redox centers/channels, and the ability to produce DROS.…”

Section: Explaining the Reaction Chemistry At Complex IV And The Effementioning

confidence: 99%

See 4 more Smart Citations

Murburn concept explains the acutely lethal effect of cyanide

Manoj¹

2019

Preprint

Self Cite

View full text Add to dashboard Cite

Cyanide (CN) toxicity is traditionally understood to result from its binding of hemeFe centers, thereby disrupting mitochondrial cytochrome oxidase function and oxygen utilization by other globin proteins. Recently, a diffusible reactive oxygen species (DROS) mediated reaction mechanism called murburn concept was proposed to explain mitochondrial ATP-synthesis and heat generation. Per this purview, it was theorized that CN ion-radical equilibrium dissipates the catalytically vital DROS into futile cycles, producing water. In the current study, a comparative quantitative assessment of the above two explanations is made for: (i) lethal dosage or concentrations of CN, (ii) thermodynamics and kinetics of the binding/reaction, and (iii) correlation of CN with the binding data and reaction chemistry of H2S/CO. The quantitative findings suggest that the hemeFe binding-based toxicity explanation is untenable. CN also inhibited the experimental in vitro DROS-mediated coupling of inorganic phosphate with ADP. Further, pH-dependent inhibition profiles of heme enzyme catalyzed oxidation of a phenolic (wherein an -OH group reacts with DROS to form water, quite akin to the murburn model of ATP synthesis) indicated that- (i) multiple competitive reactions in milieu controlled outcomes and (ii) low concentrations of CN cannot disrupt activity via a coordination (binding) of cyanide at the distal hemeFe. Therefore, the μM-level IC50 and the acutely lethal effect of CN on cellular respiration could be explained by the deleterious interaction of CN ion-radical equilibrium with DROS in matrix, disrupting mitochondrial ATP synthesis. This work supports the murburn explanation for cellular respiration.

show abstract

Section: Cn Binding In Physiological Regimesmentioning

confidence: 55%

Section: Cn Binding In Physiological Regimesmentioning

confidence: 99%

Section: Comparison Of Equilibrium and Kinetic Constants Of Cn With Omentioning

confidence: 99%

Section: Explaining the Reaction Chemistry At Complex IV And The Effementioning

confidence: 99%

Section: Explaining the Reaction Chemistry At Complex IV And The Effementioning

confidence: 99%

See 3 more Smart Citations

Murburn concept explains the acutely lethal effect of cyanide

Manoj¹

2019

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

Interaction of membrane‐embedded cytochrome b‐complexes with quinols: Classical Q‐cycle and murburn model

Manoj¹,

Gideon²,

Jaeken

2022

Cell Biochemistry & Function

Self Cite

View full text Add to dashboard Cite

We recently proposed a diffusible reactive (oxygen) species (DRS/DROS) based function for cytochrome b complexes (CBC) and quinones (Q)/quinols (QH2) in the murburn model of bioenergetics. This proposal is in direct conflict with the classical purview of Q‐cycle. Via extensive analyses of the structure‐function correlations of membrane‐quinones/quinols and proteins, we present qualitative and quantitative arguments to infer that the classical model cannot explain the energetics, kinetics, mechanism and probabilistic considerations. Therefore, it is proposed that Q‐cycle is neither necessary nor feasible at CBCs. In contrast, we substantiate that the murburn model explains: (a) crucial structural data of CBCs, (b) why quinones/quinols are utilized in bioenergetic membranes, (c) how trans‐membrane potential is generated owing to effective charge separation at CBCs, (d) mobility data of O2, DRS, Q/QH2, and (e) utility of other reaction/membrane components. Further, the murburn model also accommodates the absence of quinones in anaerobic Archaea, wherein methanophenazines are prevalent. The work mandates that the textbooks and research agendas are refreshed to reflect the new perception. Significance The current article must be seen as a critical and detailed analysis of the role and working mechanism of quinone (Q) /quinols (QH2) in bioenergetic membranes. In the classical model, QH2 are perceived as highly mobile electron‐transport agents that bind and donate electrons to cytochrome b complexes (CBCs), using sophisticated electronic circuitries, in order to recycle Q and pump protons. The classical perception sees radicals (such as Q*‐, O2*‐, etc., also called diffusible reactive species, DRS) as wasteful or toxic (patho) physiological manifestations. It is highlighted herein that QH2 has low mobility and matrix has little protons to pump. New insights from the structural analyses of diverse CBCs and quinols, in conjunction with murburn reaction thermodynamics suggest that the electrons from substrates/quinols are effectively utilized via DRS. This perception fits into a much broader analysis of 1 and 2 electron transfers in overall redox metabolism, as recently brought out by the murburn model, wherein DRS are considered obligatory ingredients of physiology. Thus, the findings mandate a reorientation in the pertinent research field.

show abstract

Why do cells need oxygen? Insights from mitochondrial composition and function

Manoj¹,

Gideon²,

Jaeken

2021

Cell Biology International

Self Cite

View full text Add to dashboard Cite

Mitochondrial membrane‐embedded redox proteins are classically perceived as deterministic “electron transport chain” (ETC) arrays cum proton pumps; and oxygen is seen as an “immobile terminal electron acceptor.” This is untenable because: (1) there are little free protons to be pumped out of the matrix; (2) proton pumping would be highly endergonic; (3) ETC‐chemiosmosis‐rotary ATP synthesis proposal is “irreducibly complex”/”non‐evolvable” and does not fit with mitochondrial architecture or structural/distribution data of the concerned proteins/components; (4) a plethora of experimental observations do not conform to the postulates/requisites; for example, there is little evidence for viable proton‐pumps/pH‐gradient in mitochondria, trans‐membrane potential (TMP) is non‐fluctuating/non‐trappable, oxygen is seen to give copious “diffusible reactive (oxygen) species” (DRS/DROS) in milieu, etc. Quite contrarily, the newly proposed murburn model's tenets agree with known principles of energetics/kinetics, and builds on established structural data and reported observations. In this purview, oxygen is needed to make DRS, the principal component of mitochondrial function. Complex V and porins respectively serve as proton‐inlet and turgor‐based water‐exodus portals, thereby achieving organellar homeostasis. Complexes I to IV possess ADP‐binding sites and their redox‐centers react/interact with O2/DRS. At/around these complexes, DRS cross‐react or activate/oxidize ADP/Pi via fast thermogenic one‐electron reaction(s), condensing to form two‐electron stabilized products (H2O2/H2O/ATP). The varied architecture and distribution of components in mitochondria validate DRS as (i) the coupling agent of oxidative reactions and phosphorylations, and (ii) the primary reason for manifestation of TMP in steady‐state. Explorations along the new precepts stand to provide greater insights on mitochondrial function and pathophysiology.

show abstract

Atypical profiles and modulations of heme-enzymes catalyzed outcomes by low amounts of diverse additives suggest diffusible radicals' obligatory involvement in such redox reactions

Cited by 58 publications

References 61 publications

Murburn concept explains the acutely lethal effect of cyanide

Murburn concept explains the acutely lethal effect of cyanide

Interaction of membrane‐embedded cytochrome b‐complexes with quinols: Classical Q‐cycle and murburn model

Why do cells need oxygen? Insights from mitochondrial composition and function

Contact Info

Product

Resources

About