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Purification and properties of the soluble carnitine palmitoyltransferase from bovine liver mitochondria.

ABSTRACT: A new carnitine palmitoyltransferase (CPT) was purified to homogeneity from bovine liver mitochondria which were 96% free of peroxisomal contamination, as judged by catalase and glutamate dehydrogenase activities. The enzyme is easily removed from mitochondria, without the use of detergent. It is monomeric (Mr 63,500), unlike other preparations of CPT from mitochondria, and is most active with myristoyl-CoA and palmitoyl-CoA. The Km values are between 0.8 and 4 microM for a range of substrates from hexanoyl-CoA to stearoyl-CoA; these are much lower than values reported for other purified CPT preparations. The Km for L-carnitine is 185 microM measured with palmitoyl-CoA, and does not vary greatly with the chain length. This is also lower than the values reported for other CPT preparations, but higher than those cited for the medium-chain transferases. Kinetic and inhibitor studies were consistent with a rapid-equilibrium random-order mechanism. 2-Bromopalmitoyl-CoA, which is an inhibitor of the outer CPT, inhibited the enzyme competitively with palmitoyl-CoA as the variable substrate, when added without preincubation. If the enzyme was preincubated with 2-bromopalmitoyl-CoA and carnitine, the activity did not reappear after gel filtration of the protein. The inhibitor was bound in a 1:1 stoichiometry per subunit of enzyme.

SUBMITTER: Ramsay RR

PROVIDER: S-EPMC1147987 | biostudies-other | 1987 Jun

REPOSITORIES: biostudies-other

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Carnitine palmitoyltransferase 1C regulates cancer cell senescence through mitochondria-associated metabolic reprograming.

Project description:Cellular senescence is a fundamental biological process that has profound implications in cancer development and therapeutics, but the underlying mechanisms remain elusive. Here we show that carnitine palmitoyltransferase 1C (CPT1C), an enzyme that catalyzes carnitinylation of fatty acids for transport into mitochondria for ?-oxidation, plays a major role in the regulation of cancer cell senescence through mitochondria-associated metabolic reprograming. Metabolomics analysis suggested alterations in mitochondria activity, as revealed by the marked decrease in acylcarnitines in senescent human pancreatic carcinoma PANC-1 cells, indicating low CPT1C activity. Direct analyses of mRNA and protein show that CPT1C is significantly reduced in senescent cells. Furthermore, abnormal mitochondrial function was observed in senescent PANC-1 cells, leading to lower cell survival under metabolic stress and suppressed tumorigenesis in a mouse xenograft model. Knock-down of CPT1C in PANC-1 cells induced mitochondrial dysfunction, caused senescence-like growth suppression and cellular senescence, suppressed cell survival under metabolic stress, and inhibited tumorigenesis in vivo. Further, CPT1C knock-down suppressed xenograft tumor growth in situ. Silencing of CPT1C in five other tumor cell lines also caused cellular senescence. On the contrary, gain-of-function of CPT1C reversed PANC-1 cell senescence and enhanced mitochondrial function. This study identifies CPT1C as a novel biomarker and key regulator of cancer cell senescence through mitochondria-associated metabolic reprograming, and suggests that inhibition of CPT1C may represent a new therapeutic strategy for cancer treatment through induction of tumor senescence.

| S-EPMC5864250 | biostudies-literature

Carnitine palmitoyltransferase activities (EC 2.3.1.-) of rat liver mitochondria.

Project description:1. A continuously recording and sensitive fluorimetric assay is described for carnitine palmitoyltransferase. This assay has been applied to whole or disintegrated mitochondria and to soluble protein fractions. 2. When rat liver mitochondria had been disintegrated by ultrasound, the specific activity of carnitine palmitoyltransferase was 15-20m-units/mg of protein. Only one-fifth of this activity was assayable (with added substrates) before mitochondrial disintegration. 3. It is concluded that there are two carnitine palmitoyltransferase activities in rat liver mitochondria, of which one (type I) is relatively superficial in location and catalyses an acyl-group transfer between added CoA and carnitine, whereas the other (type II) is less superficial and catalyses an acyl-group transfer in unbroken mitochondria between added carnitine and intramitochondrial CoA. The existence of two distinct carnitine palmitoyltransferases was predicted by Fritz & Yue (1963). 4. In unbroken mitochondria, type I transferase is accessible to the inhibitor 2-bromostearoyl-CoA whereas the type II transferase is inaccessible. 5. A major part of the total carnitine palmitoyltransferase activity of rat liver mitochondria is membrane-bound and of type II. 6. These observations, when considered in conjunction with the penetration of mitochondria by CoASH or carnitine, indicate that the type II transferase is attached to the inner mitochondrial membrane.

| S-EPMC1179386 | biostudies-other

Restoration of the properties of carnitine palmitoyltransferase I in liver mitochondria during re-feeding of starved rats.

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| S-EPMC1147307 | biostudies-other

The soluble carnitine palmitoyltransferase from bovine liver. A comparison with the enzymes from peroxisomes and from the mitochondrial inner membrane.

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| S-EPMC1148690 | biostudies-other

Acute liver carnitine palmitoyltransferase I overexpression recapitulates reduced palmitate oxidation of cardiac hypertrophy.

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Carnitine palmitoyltransferase II deficiency: successful anaplerotic diet therapy.

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Carnitine Palmitoyltransferase 1A Has a Lysine Succinyltransferase Activity.

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Carnitine palmitoyltransferase 1C contributes to progressive cellular senescence.

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Cholestatic Jaundice Associated with Carnitine Palmitoyltransferase IA Deficiency.

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| S-EPMC3575043 | biostudies-literature

Regulation by oestrogen of carnitine palmitoyltransferase in hepatic mitochondria.

Project description:Treatment of female rats with ethynyloestradiol decreased both the activity of carnitine palmitoyltransferase and its Ki value for malonyl-CoA compared with pair-fed control rats. In starved rats, carnitine palmitoyltransferase activity and its Ki value for malonyl-CoA were both elevated as expected. Oestrogen treatment had no effect on carnitine palmitoyltransferase activity in the starved state, but the Ki value for malonyl-CoA was substantially decreased by oestrogen. Treatment with a more physiological concentration of ethynyloestradiol (15 micrograms/kg body wt. per day) also produced a decrease in the Ki value for malonyl-CoA. These data suggest that the oestrogen may produce its anti-ketogenic effect by increasing the affinity of carnitine palmitoyltransferase for its physiological inhibitor, malonyl-CoA.

| S-EPMC1147025 | biostudies-other

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