Evidence against in vitro modulation of rat liver cholesterol 7 alpha-hydroxylase activity by phosphorylation-dephosphorylation: comparison with hydroxymethylglutaryl CoA reductase.

Lars Berglund, I. Björkhem, B. Angelin, K. Einarsson

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Abstract

The activity of cholesterol 7 alpha-hydroxylase in rat liver microsomes was investigated under conditions favourable for phosphorylation-dephosphorylation. The enzyme activity was similar in the presence or absence of sodium fluoride during preparation. Preincubation with ATP and magnesium did not affect the enzyme activity. Cholesterol 7 alpha-hydroxylase was inhibited by alkaline phosphatase, but this inhibition was similar also after inactivation of the phosphatase. Under similar conditions, rat hepatic hydroxymethylglutaryl CoA reductase activity was clearly modulated in agreement with phosphorylation-dephosphorylation. The absence of such a modulation of cholesterol 7 alpha-hydroxylase argues against involvement of phosphorylation-dephosphorylation in the regulation of this enzyme.

Original languageEnglish (US)
Pages (from-to)457-461
Number of pages5
JournalActa chemica Scandinavica. Series B: Organic chemistry and biochemistry
Volume40
Issue number6
StatePublished - Jul 1986
Externally publishedYes

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Cholesterol 7-alpha-Hydroxylase
Hydroxymethylglutaryl CoA Reductases
Phosphorylation
Liver
Enzymes
Sodium Fluoride
Liver Microsomes
Phosphoric Monoester Hydrolases
Magnesium
Alkaline Phosphatase
Adenosine Triphosphate
In Vitro Techniques

ASJC Scopus subject areas

  • Medicine(all)

Cite this

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title = "Evidence against in vitro modulation of rat liver cholesterol 7 alpha-hydroxylase activity by phosphorylation-dephosphorylation: comparison with hydroxymethylglutaryl CoA reductase.",
abstract = "The activity of cholesterol 7 alpha-hydroxylase in rat liver microsomes was investigated under conditions favourable for phosphorylation-dephosphorylation. The enzyme activity was similar in the presence or absence of sodium fluoride during preparation. Preincubation with ATP and magnesium did not affect the enzyme activity. Cholesterol 7 alpha-hydroxylase was inhibited by alkaline phosphatase, but this inhibition was similar also after inactivation of the phosphatase. Under similar conditions, rat hepatic hydroxymethylglutaryl CoA reductase activity was clearly modulated in agreement with phosphorylation-dephosphorylation. The absence of such a modulation of cholesterol 7 alpha-hydroxylase argues against involvement of phosphorylation-dephosphorylation in the regulation of this enzyme.",
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T1 - Evidence against in vitro modulation of rat liver cholesterol 7 alpha-hydroxylase activity by phosphorylation-dephosphorylation

T2 - comparison with hydroxymethylglutaryl CoA reductase.

AU - Berglund, Lars

AU - Björkhem, I.

AU - Angelin, B.

AU - Einarsson, K.

PY - 1986/7

Y1 - 1986/7

N2 - The activity of cholesterol 7 alpha-hydroxylase in rat liver microsomes was investigated under conditions favourable for phosphorylation-dephosphorylation. The enzyme activity was similar in the presence or absence of sodium fluoride during preparation. Preincubation with ATP and magnesium did not affect the enzyme activity. Cholesterol 7 alpha-hydroxylase was inhibited by alkaline phosphatase, but this inhibition was similar also after inactivation of the phosphatase. Under similar conditions, rat hepatic hydroxymethylglutaryl CoA reductase activity was clearly modulated in agreement with phosphorylation-dephosphorylation. The absence of such a modulation of cholesterol 7 alpha-hydroxylase argues against involvement of phosphorylation-dephosphorylation in the regulation of this enzyme.

AB - The activity of cholesterol 7 alpha-hydroxylase in rat liver microsomes was investigated under conditions favourable for phosphorylation-dephosphorylation. The enzyme activity was similar in the presence or absence of sodium fluoride during preparation. Preincubation with ATP and magnesium did not affect the enzyme activity. Cholesterol 7 alpha-hydroxylase was inhibited by alkaline phosphatase, but this inhibition was similar also after inactivation of the phosphatase. Under similar conditions, rat hepatic hydroxymethylglutaryl CoA reductase activity was clearly modulated in agreement with phosphorylation-dephosphorylation. The absence of such a modulation of cholesterol 7 alpha-hydroxylase argues against involvement of phosphorylation-dephosphorylation in the regulation of this enzyme.

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