PM-pathway control state

high-resolution terminology - matching measurements at high-resolution

PM-pathway control state

Description

PM: Pyruvate & Malate.

MitoPathway control: CI

SUIT protocol: SUIT RP1

Pyruvate (P) is oxidatively decarboxylated to acetyl-CoA and CO₂, yielding NADH catalyzed by pyruvate dehydrogenase. Malate (M) is oxidized to oxaloacetate by mt-malate dehydrogenase located in the mitochondrial matrix. Condensation of oxaloacate with acetyl-CoA yields citrate (citrate synthase). 2-oxoglutarate (α-ketoglutarate) is formed from isocitrate (isocitrate dehydrogenase).

Abbreviation: PM

Reference: Gnaiger 2014 MitoPathways - Chapter 3.2

MitoPedia concepts: Respiratory state, SUIT state 

PM(L)

• SUIT RP1: 1PM 2D 2c (2NADH) 3U 4Oct 5G 6S 7Rot 8Gp 9Ama 10Tm

PM(P)

• SUIT RP1: 1PM 2D 2c (2NADH) 3U 4Oct 5G 6S 7Rot 8Gp 9Ama 10Tm

PM(E)

• SUIT RP1: 1PM 2D 2c (2NADH) 3U 4Oct 5G 6S 7Rot 8Gp 9Ama 10Tm

CI-linked linear coupling control: L – P - E

• L - P

OXPHOS coupling efficiency (P-L or ≈P control factor), j_≈P = ≈P/P = (P-L)/P = 1-L/P, is measured in the CI-linked substrate state, with defined coupling sites (CI, CIII, CIV) and at high flux.

• P - E

CCCP is titrated stepwise to maximum flux, to evaluate limitation of OXPHOS by the phosphorylation system, expressed as the apparent excess E-P capacity factor (E-P coupling control factor), j_ExP = (E-P)/E = 1-P/E. If j_ExP>0, then the ETS coupling efficiency rather than the OXPHOS coupling efficiency is the proper expression of coupling, j_≈E = ≈E/E = (E-L)/E = 1-L/E.

Discussion

Pyruvate alone is not an ETS competent substrate state in most mt-preparations, since acetyl-CoA accumulates without the co-substrate (oxaloacetate) of citrate synthase.

Malate alone is not an ETS competent substrate state in many mt-preparations, since oxaloacetate accumulates without the co-substrate (acetyl-CoA) of citrate synthase.