ETS pathway types: Difference between revisions

Revision as of 20:28, 10 February 2016

high-resolution terminology - matching measurements at high-resolution

ETS pathway types

Description

Substrate types in SUIT protocols are types of reduced substrates feeding electrons into the electron transfer system (ETS) at different levels of mitochondrial pathways.

Substrates of type 4 feed electrons into dehydrogenases and enzyme systems upstream of the type 3 pathway level. Succinate does not belong to the type 4 substrates. Electron transfer from type 4 substrates (N and F) converges at the NADH-junction and FADH₂-junction (N- and F-junction). Representative type N substrates are pyruvate, glutamate and malate, whrease type F substrates are fatty acids. Fatty acid oxidation (FAO) not only depends on electron transfer through the F-junction (which is typically rate-limiting) but simultaneously requires N-junction throughput, hence FAO can be inhibited completely by inhibition of Complex I (CI).

Substrates of type 3 (e.g. succinate, glycerophosphate) feed electrons into respiratory complexes upstream of the Q-junction. Note that succinate is the substrate for succinate dehydrogenase (SDH), whereas FADH₂ is the product of SDH. In contrast, FADH₂ is the substrate of electron transferring flavoprotein (CETF).

Substrates of type 2 feed electrons into Complex III (CIII) with further electron transfer downstream of the Q-junction.

Substrates of type 1 may be artificial electron donors (e.g. TMPD, Tm) essentially bypassing the ETS and feeding electrons directly into the terminal electron acceptor, cytochrome c oxidase (CIV) or alternative oxidases (single enzymatic step).

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MitoPedia topics: Substrate and metabolite

Contributed by Gnaiger E 2016-02-01

Substrate types on different pathway levels

Substrate types on the pathway level of converging NADH- and FADH₂-linked dehydrogenases, including the TCA cycle and beta-oxidation:

N: NADH-linked substrates (CI-linked)

F: FADH₂-linked substrates (FAO)

Substrate types on the pathway level of electron transfer complexes converging at the Q-junction:

S: Succinate (CII-linked)

Gp: Glycerophosphate (CGpDH-linked)

Substrate types on the single step level of cytochrome c oxidase (CIV), the terminal step in the aerobic electron transfer system:

Tm: Artificial electron transfer susbstrate TMPD (Tm) maintained in a reduced state by ascorbate (As) and reducing cytochrome c as the substrate of CIV.

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-'''Substrate types''' in SUIT protocols are types of reduced substrates feeding electrons into the [[electron transfer system]] (ETS) at different levels of mitochondrial pathways. Substrates of type 1 may be artificial electron donors essentially bypassing the ETS and feeding electrons directly into the terminal electron acceptor, cytochrome c oxidase (CIV) or alternative oxidases (single enzymatic step). Substrates of type 2 feed electrons into Complex III (CIII) with further electron transfer downstream of the [[Q-junction]]. Substrates of type 3 feed electrons into respiratory complexes directly upstream of the Q-junction, whereas substrates of type 4 feed electrons into dehydrogenases and enzyme systems upstream of the type 3 pathway level.
+'''Substrate types''' in SUIT protocols are types of reduced substrates feeding electrons into the [[electron transfer system]] (ETS) at different levels of mitochondrial pathways.
+Substrates of '''type 4''' feed electrons into dehydrogenases and enzyme systems upstream of the type 3 pathway level. Succinate does not belong to the type 4 substrates. Electron transfer from type 4 substrates (N and F) converges at the NADH-junction and FADH<sub>2</sub>-junction (N- and F-junction). Representative '''type N substrates''' are pyruvate, glutamate and malate, whrease '''type F substrates''' are fatty acids. Fatty acid oxidation (FAO) not only depends on electron transfer through the F-junction (which is typically rate-limiting) but simultaneously requires N-junction throughput, hence FAO can be inhibited completely by inhibition of Complex I (CI).
+Substrates of '''type 3''' (e.g. [[succinate]], [[glycerophosphate]]) feed electrons into respiratory complexes upstream of the [[Q-junction]]. Note that succinate is the substrate for [[succinate dehydrogenase]] (SDH), whereas FADH<sub>2</sub> is the ''product'' of SDH. In contrast, FADH<sub>2</sub> is the ''substrate'' of [[electron transferring flavoprotein]] (CETF).
+Substrates of type 2 feed electrons into Complex III (CIII) with further electron transfer downstream of the [[Q-junction]].
+Substrates of '''type 1''' may be artificial electron donors (e.g. TMPD, Tm) essentially bypassing the ETS and feeding electrons directly into the terminal electron acceptor, cytochrome ''c'' oxidase (CIV) or alternative oxidases (single enzymatic step).
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 {{MitoPedia concepts