Taurine, Glutathione and Bioenergetics - Advances in Experimental Medicine and Biology - page 9

Acetyl-CoA

NADPH
/ NADP +

Glutathione
reductase

Tricarboxylic
acid cycle

Transhydro-
genase

GSH / GSSG

NADH / NAD +

Matrix pH buffering
by taurine

Electron transport chain
Proton pumping

Proton gradient

Electrical gradient

ATP synthase

ATP

Fig. 1.3 Simplified model for mitochondrial function. The proton gradient is built up by the tri-
carboxylic acid cycle and subsequent electron transport chain. Simultaneously, the electrical gradi-
ent is established through a redox equilibrium between NADH/NAD + and the redox buffer GSH/
GSSG. Several of these processes are stabilised by taurine as matrix pH buffer. The proton and
electrical gradients drive together the ATP production by ATP synthase and associated proton
movement

is the pH dependence of free radical and ROS formation (Selivanov et al. 2008 ) .
But also the roles of mitochondrial thiols in antioxidant scavenging and redox
signalling have to be dealt with (Murphy 2012 ) .
Further perspectives on mitochondrial function could be based on the increased
reactivity of thiols and GSH with increasing pH. Consequently, the reported open-
ing of mitochondrial ion channels or opening of the uncoupling proteins (UCP) due
to GSH redox status or glutathionylation (Aon et al. 2007 ; Slodzinski et al. 2008 ;
Mailloux et al. 2011 ) could be a direct response to increased pH in the matrix. That
is the increased tendency to glutathionylation protects the matrix from excessive
alkalinisation by opening the UCPs for incoming protons.
The consequence of taurine depletion on mitochondrial function has been dis-
cussed elsewhere (Hansen et al. 2010 ; Jong et al. 2012 ), as well as the results of
GSH deficiency or depletion (Meister 1995 ; Aon et al. 2007 ). However, the ele-
ments in the presented model with focus on the interplay between taurine and GSH
need to be included when analysing mitochondrial function and dysfunction, e.g. in
diabetes (Hansen 2001 ; Hansen et al. 2010 ). Currently, the two compounds are
hardly introduced in even advanced presentations or calculation models of mito-
chondrial function and bioenergetics.