Electron-transfer-pathway state

high-resolution terminology - matching measurements at high-resolution

Electron-transfer-pathway state

Description

Substrate control states are obtained in mitochondrial preparations (isolated mitochondria, permeabilized cells, permeabilized tissues, tissue homogenate) by depletion of endogenous substrates and addition of specific substrates to the mitochondrial respiration medium. Mitochondrial substrate control states have to be defined complementary to mitochondrial coupling control states.

1. Substrate control states with electron entry through a single respiratory Complex (electron gaiting);
2. Physiological substrate control states with convergent electron flow.

Abbreviation: n.a.

Reference: Gnaiger 2009 Int J Biochem Cell Biol

MitoPedia methods: Respirometry 

MitoPedia topics: "Respiratory state" is not in the list (Enzyme, Medium, Inhibitor, Substrate and metabolite, Uncoupler, Sample preparation, Permeabilization agent, EAGLE, MitoGlobal Organizations, MitoGlobal Centres, ...) of allowed values for the "MitoPedia topic" property. Respiratory state"Respiratory state" is not in the list (Enzyme, Medium, Inhibitor, Substrate and metabolite, Uncoupler, Sample preparation, Permeabilization agent, EAGLE, MitoGlobal Organizations, MitoGlobal Centres, ...) of allowed values for the "MitoPedia topic" property. 

Control by substrate type: Pathway control states

A: Intact cells

Endogenous or exogenous substrate control.

B: Mitochondrial preparations

Specific substrate-inhibitor combinations are selected to establish substrate states for (i) stimulating defined segments of the electron transfer system, or (ii) reconstitution of TCA cycle function.

1. Substrate control states with electron gaiting: Specific substrate-inhibitor combinations are applied for selectively stimulating electron entry though Complex I, CII, or other branches converging at the Q-junction, particularly with fatty acids and alpha-glycerophosphate (CI respiration, CII respiration, etc.). The most commonly applied substrate states select for Complex I electron input (CI: pyruvate+malate, PM; glutamate+malate, GM), Complex II electron input (CII: succinate+rotenone, S(Rot)), or Complex IV electron input (CIV: ascorbate+TMPD(Ama)).
2. Physiological substrate control states: Reconstitution of TCA cycle function requires CI+II-linked substrate combinations, such as PMS, GMS, or PMGS, applied simultaneously without inhibitor of any respiratory complexes.

Control by substrate concentration: Kinetic control states

1. Kinetic substrate or adenylate control: Kinetic studies with variation of a specific substrate (reduced substrate supplying electrons to the ETS; ADP, Pi; O₂; cytochrome c) are analyzed by kinetic functions (e.g. hyperbolic), yielding apparent kinetic constants, such as J_max, K_m', c₅₀, or p₅₀.
2. Kinetic inhibitor control: Kinetic studies with variation of a specific inhibitor yield apparent kinetic constants, such as the K_I'.