5-Hydroxydecanoate is metabolised in mitochondria and creates a rate-limiting bottleneck for beta-oxidation of fatty acids.
5-Hydroxydecanoate (5-HD) blocks pharmacological and ischaemic preconditioning, and has been postulated to be a specific inhibitor of mitochondrial ATP-sensitive K(+) (K(ATP)) channels. However, recent work has shown that 5-HD is activated to 5-hydroxydecanoyl-CoA (5-HD-CoA), which is a substrate for the first step of beta-oxidation. We have now analysed the complete beta-oxidation of 5-HD-CoA using specially synthesised (and purified) substrates and enzymes, as well as isolated rat liver and heart mitochondria, and compared it with the metabolism of the physiological substrate decanoyl-CoA. At the second step of beta-oxidation, catalysed by enoyl-CoA hydratase, enzyme kinetics were similar using either decenoyl-CoA or 5-hydroxydecenoyl-CoA as substrate. The last two steps were investigated using l-3-hydroxyacyl-CoA dehydrogenase (HAD) coupled to 3-ketoacyl-CoA thiolase. V(max) for the metabolite of 5-HD (3,5-dihydroxydecanoyl-CoA) was fivefold slower than for the corresponding metabolite of decanoate (l-3-hydroxydecanoyl-CoA). The slower kinetics were not due to accumulation of d-3-hydroxyoctanoyl-CoA since this enantiomer did not inhibit HAD. Molecular modelling of HAD complexed with 3,5-dihydroxydecanoyl-CoA suggested that the 5-hydroxyl group could decrease HAD turnover rate by interacting with critical side chains. Consistent with the kinetic data, 5-hydroxydecanoyl-CoA alone acted as a weak substrate in isolated mitochondria, whereas addition of 100 mum 5-HD-CoA inhibited the metabolism of decanoyl-CoA or lauryl-carnitine. In conclusion, 5-HD is activated, transported into mitochondria and metabolised via beta-oxidation, albeit with rate-limiting kinetics at the penultimate step. This creates a bottleneck for beta-oxidation of fatty acids. The complex metabolic effects of 5-HD invalidate the use of 5-HD as a blocker of mitochondrial K(ATP) channels in studies of preconditioning.
Hanley
Peter J
PJ
Institut für Normale und Pathologische Physiologie, Universität Marburg, Deutschhausstrasse 2, 35037 Marburg, Germany. hanley@mailer.uni-marburg.de
Dröse
Stefan
S
Brandt
Ulrich
U
Lareau
Rachel A
RA
Banerjee
Abir L
AL
Srivastava
D K
DK
Banaszak
Leonard J
LJ
Barycki
Joseph J
JJ
Van Veldhoven
Paul P
PP
Daut
Jürgen
J
D000818:Animals; D001711:Biotransformation; D003065:Coenzyme A / Q000378:metabolism; D003652:Decanoic Acids / Q000378:metabolism* / Q000493:pharmacokinetics; D004952:Esters / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism* / Q000493:pharmacokinetics; D006880:Hydroxy Acids / Q000378:metabolism* / Q000493:pharmacokinetics; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000201:enzymology / Q000378:metabolism; D008930:Mitochondria, Liver / Q000201:enzymology / Q000378:metabolism; D008958:Models, Molecular; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats
D003652:Decanoic Acids; D004952:Esters; D005227:Fatty Acids; D006880:Hydroxy Acids; D009243:NAD; C052853:5-hydroxydecanoic acid; D003065:Coenzyme A