Open AccessRedox control of β‐oxidation in rat liver mitochondria
Author(s) -
EATON Simon,
TURNBULL Douglass M.,
BARTLETT Kim
Publication year - 1994
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1994.tb18668.x
Subject(s) - nad+ kinase , carnitine , chemistry , mitochondrion , biochemistry , respiratory chain , redox , flavoprotein , beta oxidation , flux (metallurgy) , stereochemistry , metabolism , enzyme , organic chemistry
Coupled rat liver mitochondria were incubated with [U‐ 14 C]hexadecanoate and carnitine which resulted in the formation of acyl‐, 2‐enoyl‐ and 3‐hydroxyacyl‐CoA and carnitine esters. The production of 2‐enoyl‐CoA and 3‐hydroxyacyl‐CoA esters was associated with a significant lowering of the NAD + /NADH ratio, in contrast to rat muscle mitochondria [Eaton, S., Bhuiyan, A. K. M. J., Kler, R. S., Turnbull, D. M. & Bartlett, K. (1993) Biochem. J. 289 , 161–172], suggesting that control by the respiratory chain is important under normal conditions. When NAD + /NADH ratios were held low by succinate‐induced reverse electron flow, 3‐enoyl‐CoA esters were also detected, probably formed by the action of 3,2‐enoyl‐CoA isomerase. Measurement of the flux of ß‐oxidation at different osmolalities showed that flux was strongly dependent on osmolality changes in the physiological range. Measurement of the CoA and carnitine esters resulting from incubations made at different osmolalities showed that there was an increase in the amounts of the saturated acyl‐CoA esters with respect to 2‐enoyl‐CoA and 3‐hydroxyacyl‐CoA esters, consistent with control by the electron‐transfer flavoprotein‐ubiquinone segment [Halestrap, A. P. & Dunlop, J. L. (1986) Biochem. J. 239 , 559–565]. This however could not be the only factor operating as indicated by the continued presence of 2‐enoyl‐CoA and 3‐hydroxyacyl‐CoA esters at high osmolalities.