API

Event: 1543

Key Event Title

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Mitochondrial Complex IV inhibition

Short name

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Mitochondrial Complex IV inhibition

Biological Context

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Level of Biological Organization
Molecular

Cell term

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Organ term

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Key Event Components

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Process Object Action

Key Event Overview


AOPs Including This Key Event

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AOP Name Role of event in AOP
Mitochondrial complex inhibition leading to liver injury MolecularInitiatingEvent

Stressors

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Taxonomic Applicability

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Life Stages

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Sex Applicability

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Key Event Description

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The mitochondrial complex IV (Cytochrome c oxidase) is an enzyme complex located in the inner membrane of mitochondria. It is the forth out of 5 complexes that together form the mitochondrial respiratory chain. It consists out of multiple subunits of cytochrome c oxidase, including cytochrome a and cytochrome a3.

The combination of these subunits catalyze following process:

  1. The cytochrome c oxidase is involved in the process of oxidizing reduced cytochrome c to its oxidized form. A process that results in a free electron.

  1. 4 oxidation rounds results in enough electron to reduce 1 molecule oxygen to 2 molecules water.

 

The electron transfer in this process mediates the translocation of protons from the mitochondrial matrix through the inner membrane to the intermembrane space. The created proton gradient will be used to catalyze the reaction in which ADP is converted into ATP.

 

The initiation event is the reversibly or irreversibly interaction to any of the subunits in the mitochondrial complex IV, leading to an perturbation of the electron flow and an absence of proton transport via this complex.


How It Is Measured or Detected

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  1. Complex inhibition assays specifically for complex IV
    The activity of complex IV is always tested in the bovine heart mitochondria provided within the kit. The kit relies on the following detection of complex IV activity:
    The reduction of cytochrome c, which leads to a reduction in absorbance at 550nm can be measured.

  2. Mitochondrial Membrane potential using fluorescent dyes.
    Positive charged molecules will accumulated in the mitochondria in an inverse proportion as the membrane potential. More polarised mitochondria will accumulate more dye (Rhodamine123, TMRE, TMRM) - leading to a higher fluorescent signal - and the absence of membrane potential leads to an absence of fluorescent signal. An exception is the dye JC1, because this dye has green fluorescence when present in low concentrations (depolarisation) and red fluorescence when accumulated (hyperpolarized

 

Measurements

Complex inhibition assays

  1. Cayman MitoCheck
    MitoCheck® Complex IV Activity Assay Kit (Item No. 700990)

  2. Abcam
    MitoTox™ Complex IV OXPHOS Activity Assay Kit (ab109906)
    Complex IV Human Enzyme Activity Microplate Assay Kit (ab109909)

  3. BioVision
    Cytochrome Oxidase Activity Colorimetric Assay Kit (K287)

Membrane potential dyes

  1. Perry, 2011, mitochondrial membrane potential probes and proton gradient

  2. Mitra, 2010, analysis of mitochondrial dynamics and functions using imaging approaches


Domain of Applicability

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Evidence for Perturbation by Stressor


Overview for Molecular Initiating Event

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References

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