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The oxoacyl-coenzyme A thiolases of animal tissues.

ABSTRACT: 1. The activities and relative 3-oxoacyl-CoA substrate specificities of oxoacyl-CoA thiolase were determined in a large number of animal tissues. The relative activities with different 3-oxoacyl-CoA substrates varied widely in different tissues and, in addition, the activity as measured with acetoacetyl-CoA (but not with other longer-carbon-chain acyl-CoA substrates) was activated by K(+). 2. These properties were due to the presence, in different proportions in each tissue, of three classes of thiolase, all of which use acetoacetyl-CoA as substrate but which have different intracellular locations and substrate specificities and which differ also in kinetic and chromatographic behaviour. 3. Cytoplasmic thiolase activity was found to be widely distributed among different tissues and was due to an acetoacetyl-CoA-specific thiolase. This cytoplasmic activity was found to account for a significant proportion of the total tissue activity towards acetoacetyl-CoA in several tissues, and especially in the brain of newborn rats. 4. Mitochondrial thiolase activity towards acetoacetyl-CoA was due to two different classes of enzyme whose relative amounts varied with the tissue type. An oxoacyl-CoA thiolase of general specificity for the acyl-CoA substrate constituted one class, the other being a specific acetoacetyl-CoA thiolase that differed from its cytoplasmic counterpart in being greatly stimulated by K(+). 5. This activation by K(+) made it possible to calculate the tissue contents of mitochondrial acetoacetyl-CoA thiolase and mitochondrial oxoacyl-CoA thiolase from measurements of activity with acetoacetyl-CoA in tissue extracts under defined conditions. 6. The properties and the different thiolases and their tissue distribution is discussed with respect to their possible roles in metabolism.

SUBMITTER: Middleton B

PROVIDER: S-EPMC1177647 | biostudies-other | 1973 Apr

REPOSITORIES: biostudies-other

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Project description:Our present study reveals significant decelerating effects on senescence processes in middle-aged SAMP1 mice supplemented for 6 or 14 months with the reduced form (QH2, 500 mg/ kg BW/ day) of coenzyme Q10 (CoQ10). To unravel molecular mechanisms of these CoQ10 effects, a genome-wide transcript profiling in liver, heart, brain and kidney of SAMP1 mice supplemented with the reduced (QH2) or oxidized form of CoQ10 (Q10) was performed. Liver seems to be the main target tissue of CoQ10 intervention, followed by kidney, heart and brain. Stringent evaluation of the resulting data revealed that QH2 has a stronger impact on gene expression than Q10, which was primarily due to differences in the bioavailability. Indeed, we found that QH2 supplementation was more effective than Q10 to increase levels of CoQ10 in the liver of SAMP1 mice (54.92-fold and 30.36-fold, respectively). To identify functional and regulatory connections of the âtop 50â (p < 0.05) up- and down-regulated QH2-sensitive transcripts in liver (fold changes ranging from 21.24 to -6.12), text mining analysis (Genomatix BiblioSphere, GFG level B3) was used. Hereby, we identified 11 QH2-sensitive genes which are regulated by PPAR-Î± and are primarily involved in cholesterol synthesis (e.g. HMGCS1, HMGCL, HMGCR), fat assimilation (FABP5), lipoprotein metabolism (PLTP) and inflammation (STAT-1). Thus, we provide evidence that QH2 is involved in the reduction of fat and cholesterol synthesis via modulation of the PPAR-Î± signalling pathway. These data may explain, at least in part, the observed effects on decelerated age-dependent degeneration processes in QH2-supplemented SAMP1 mice. Whole genome expression profiles were analysed from liver, heart, brain and kidney (each analyzed separately) of SAMP1 mice supplemented with QH2, Q10 or a control diet. From every experimental group, three mice each were sacrificed 6 or 14 months after supplementation, resulting in a total of 72 microarrays.

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The oxoacyl-coenzyme A thiolases of animal tissues.

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