Fatty acyl-CoA as an endogenous activator of UDP-glucuronosyltransferases

doi:10.1016/j.bbrc.2006.05.089

Biochemical and Biophysical Research Communications

Volume 345, Issue 4, 14 July 2006, Pages 1649-1656

https://doi.org/10.1016/j.bbrc.2006.05.089 Get rights and content

Abstract

The acyl-CoA-dependent modulation of hepatic microsomal UDP-glucuronosyltransferase (UGT) function in rats was studied. Oleoyl- and palmitoyl-CoAs inhibited UGT activity toward 4-methylumbelliferone in the presence of Brij 58. However, acyl-CoAs enhanced UGT activity in untreated microsomes. A maximum activation of about 8-fold over the control was observed at 15 μM oleoyl-CoA, whereas 50 μM or more oleoyl-CoA had an inhibitory effect on UGT function. Medium- and long-chain acyl-CoAs also exhibited similar effects. On the basis of resistance to tryptic digestion of UGTs, oleoyl-CoA at 15 μM has no ability to change the permeability of the endoplasmic reticulum (ER) membrane, although perturbation of the membrane occurred with 50 μM oleoyl-CoA. N-Ethylmaleimide and 5,5′-dithiobis(2-nitrobenzoic acid) abolished the oleoyl-CoA (15 μM)-dependent activation of microsomal UGT. These results suggest that: (1) acyl-CoAs play a role as an endogenous activator of UGTs, and (2) a sulfhydryl group is required for the activation of UGT by physiological concentrations of acyl-CoAs.

Section snippets

Materials and methods

Materials. 4-Methylumbelliferone (4-MU), egg yolk l-α-phosphatidylcholine, trypsin, and trypsin inhibitor were purchased from Sigma–Aldrich (St. Louis, MO, USA). The following fatty acids and acyl-CoAs were also obtained from Sigma–Aldrich: caproyl-CoA 3Li · 3H₂O (C6:0), capryloyl-CoA Li · H₂O (C8:0), decanoyl-CoA Li · H₂O (C10:0), myristic acid/myristoyl-CoA Li (C14:0), palmitic acid/palmitoyl-CoA Li (C16:0), stearic acid/stearoyl-CoA Li (C18:0), oleoyl-CoA Li (C18:1), linoeic acid/linoleoyl-CoA Li

Acyl-CoA-dependent modulation of UGT activity: structure–effect relationship and conditions required

The effects of acyl-CoAs on hepatic microsomal UGT activity in the absence and presence of detergent were compared (Fig. 1). In this study, Brij 58 was used as a detergent for the perturbation of the microsomal membrane. The ratio of Brij 58 to microsomal protein (0.5 mg/mg protein) was confirmed to achieve the maximum activation of microsomal UGT activity (data not shown). Dose-dependent inhibition of UGT activity by oleoyl-CoA was observed in Brij 58-pre-treated microsomes. On the other hand,

Discussion

In the present study, we have provided evidence for the first time that medium- and long-chain acyl-CoAs activate UGT activity catalyzed by detergent-untreated microsomes. The optimum concentration (7.5, 15 or 22.5 μM) of acyl-CoA-dependent activation differed from the concentration (at least 30 μM) needed for its inhibitory effect (Fig. 1, Fig. 2). Long-chain acyl-CoAs consist of CoA, a hydrophilic moiety, and the hydrophobic region of the acyl chain. It is, therefore, reasonable that long-chain

Acknowledgment

This work was supported in part by a Grant-in-Aid for Scientific Research (C) (Research No. 17590128, recipient Y.I.) from the Japan Society for Promotion of Science.

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Fatty acyl-CoA as an endogenous activator of UDP-glucuronosyltransferases

Abstract

Section snippets

Materials and methods

Acyl-CoA-dependent modulation of UGT activity: structure–effect relationship and conditions required

Discussion

Acknowledgment

Arch. Biochem. Biophys.

Biochem. Pharmacol.

Pharmacol. Ther.

J. Biol. Chem.

Biochem. Pharmacol.

Biochem. Pharmacol.

Biochem. Pharmacol.

Arch. Biochem. Biophys.

Anal. Biochem.

J. Biol. Chem.

J. Biol Chem.

Biochim. Biophys. Acta

FEBS Lett.

Pharmacol. Ther.

Biochem. Pharmacol.

Biochem. Pharmacol.

Int. J. Biochem.

Nomenclature update for the mammalian UDP glycosyltransferase (UGT) gene superfamily

Pharmacogenet. Genomics

An investigation of the transverse topology of bilirubin UDP-glucuronosyltransferase in rat hepatic endoplasmic reticulum

Biochem. J.