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. 1984 Sep 1;222(2):335–342. doi: 10.1042/bj2220335

Changes in the ability of malonyl-CoA to inhibit carnitine palmitoyltransferase I activity and to bind to rat liver mitochondria during incubation in vitro. Differences in binding at 0 degree C and 37 degrees C with a fixed concentration of malonyl-CoA.

V A Zammit, C G Corstorphine, S R Gray
PMCID: PMC1144184  PMID: 6477517

Abstract

Time courses for inhibition of carnitine palmitoyltransferase (CPT) I activity in, and [14C]malonyl-CoA binding to, liver mitochondria from fed or 48 h-starved rats were obtained at 37 degrees C by using identical incubation conditions and a fixed concentration of malonyl-CoA (3.5 microM), which represents the middle of the physiological range observed previously [Zammit (1981) Biochem. J. 198, 75-83] Incubation of mitochondria in the absence of malonyl-CoA resulted in a time-dependent decrease in the ability of the metabolite instantaneously to inhibit CPT I and to bind to the mitochondria. Both degree of inhibition and binding were restored in parallel over a period of 6-8 min on subsequent addition of malonyl-CoA to the incubation medium. However, the increased inhibition of CPT I activity on addition of mitochondria directly to malonyl-CoA-containing medium was not accompanied by an increase in the amount of [14C]malonyl-CoA bound to mitochondria at 37 degrees C. Time courses for binding of [14C]malonyl-CoA performed at 0 degree C were different from those obtained at 37 degrees C. There was little loss of ability of [14C]malonyl-CoA to bind to mitochondria on incubation in the absence of the metabolite, but there was a time-dependent increase in binding on addition of mitochondria to malonyl-CoA-containing medium. It is suggested that these temperature-dependent differences between the time courses obtained may be due to the occurrence of different changes at 37 degrees C and at 0 degree C in the relative contributions of different components (with different affinities) to the binding observed at 3.5 microM-malonyl-CoA. Evidence for multi-component binding was obtained in the form of strongly curvilinear Scatchard plots for instantaneous (5s) binding of malonyl-CoA to mitochondria. Such multi-component binding would be expected from previous results on the different affinities of CPT I for malonyl-CoA with respect to inhibition [Zammit (1984) Biochem. J. 218, 379-386]. Mitochondria obtained from starved rats showed qualitatively the same time courses as those described above, with notable quantitative differences with respect both to the absolute extents of CPT I inhibition and [14C]malonyl-CoA binding achieved as well as to the time taken to attain them.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Bremer J. The effect of fasting on the activity of liver carnitine palmitoyltransferase and its inhibition by malonyl-CoA. Biochim Biophys Acta. 1981 Sep 24;665(3):628–631. doi: 10.1016/0005-2760(81)90282-4. [DOI] [PubMed] [Google Scholar]
  2. McGarry J. D., Mills S. E., Long C. S., Foster D. W. Observations on the affinity for carnitine, and malonyl-CoA sensitivity, of carnitine palmitoyltransferase I in animal and human tissues. Demonstration of the presence of malonyl-CoA in non-hepatic tissues of the rat. Biochem J. 1983 Jul 15;214(1):21–28. doi: 10.1042/bj2140021. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Robinson I. N., Zammit V. A. Sensitivity of carnitine acyltransferase I to malonly-CoA inhibition in isolated rat liver mitochondria is quantitatively related to hepatic malonyl-CoA concentration in vivo. Biochem J. 1982 Jul 15;206(1):177–179. doi: 10.1042/bj2060177. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Saggerson E. D. Carnitine acyltransferase activities in rat liver and heart measured with palmitoyl-CoA and octanoyl-CoA. Latency, effects of K+, bivalent metal ions and malonyl-CoA. Biochem J. 1982 Feb 15;202(2):397–405. doi: 10.1042/bj2020397. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Saggerson E. D., Carpenter C. A. Effects of fasting and malonyl CoA on the kinetics of carnitine palmitoyltransferase and carnitine octanoyltransferase in intact rat liver mitochondria. FEBS Lett. 1981 Sep 28;132(2):166–168. doi: 10.1016/0014-5793(81)81152-0. [DOI] [PubMed] [Google Scholar]
  6. Saggerson E. D., Carpenter C. A. The effect of malonyl-CoA on overt and latent carnitine acyltransferase activities in rat liver and adipocyte mitochondria. Biochem J. 1983 Feb 15;210(2):591–597. doi: 10.1042/bj2100591. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Stakkestad J. A., Bremer J. The outer carnitine palmitoyltransferase and regulation of fatty acid metabolism in rat liver in different thyroid states. Biochim Biophys Acta. 1983 Feb 7;750(2):244–252. doi: 10.1016/0005-2760(83)90025-5. [DOI] [PubMed] [Google Scholar]
  8. Zammit V. A. Increased sensitivity of carnitine palmitoyltransferase I activity to malonyl-CoA inhibition after preincubation of intact rat liver mitochondria with micromolar concentrations of malonyl-CoA in vitro. Biochem J. 1983 Mar 15;210(3):953–956. doi: 10.1042/bj2100953. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Zammit V. A. Regulation of hepatic fatty acid metabolism. The activities of mitochondrial and microsomal acyl-CoA:sn-glycerol 3-phosphate O-acyltransferase and the concentrations of malonyl-CoA, non-esterified and esterified carnitine, glycerol 3-phosphate, ketone bodies and long-chain acyl-CoA esters in livers of fed or starved pregnant, lactating and weaned rats. Biochem J. 1981 Jul 15;198(1):75–83. doi: 10.1042/bj1980075. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Zammit V. A. Reversible sensitization and desensitization of carnitine palmitoyltransferase I to inhibition by malonyl-CoA in isolated rat liver mitochondria. Significance for the mechanism of malonyl-CoA-induced sensitization. Biochem J. 1983 Sep 15;214(3):1027–1030. doi: 10.1042/bj2141027. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Zammit V. A. The effect of glucagon treatment and starvation of virgin and lactating rats on the rates of oxidation of octanoyl-L-carnitine and octanoate by isolated liver mitochondria. Biochem J. 1980 Aug 15;190(2):293–300. doi: 10.1042/bj1900293. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Zammit V. A. Time-dependence of inhibition of carnitine palmitoyltransferase I by malonyl-CoA in mitochondria isolated from livers of fed or starved rats. Evidence for transition of the enzyme between states of low and high affinity for malonyl-CoA. Biochem J. 1984 Mar 1;218(2):379–386. doi: 10.1042/bj2180379. [DOI] [PMC free article] [PubMed] [Google Scholar]

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