The incorporation of a 15β-hydrogen atom from the medium in cholesterol biosynthesis

1969 ◽  
Vol 0 (21) ◽  
pp. 1278-1280 ◽  
Author(s):  
M. Akhtar ◽  
A. D. Rahimtula ◽  
D. C. Wilton
Keyword(s):  
Hydrogen Atom ◽  
Cholesterol Biosynthesis

scholarly journals Incorporation of [2−14C,(5R)-5−3H1]mevalonic acid into cholesterol by a rat liver homogenate and into β-sitosterol and 28-isofucosterol by Larix decidua leaves

1969 ◽  
Vol 114 (4) ◽  
pp. 885-892 ◽  
Author(s):  
L J Goad ◽  
G. F. Gibbons ◽  
Loretta M. Bolger ◽  
H H Rees ◽  
T W Goodwin
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Rat Liver ◽  
Cholesterol Biosynthesis ◽  
Liver Homogenate ◽  
Mevalonic Acid ◽  
Atomic Ratio ◽  
Larix Decidua ◽  
Tritium Atom

1. Incubation of a rat liver homogenate with 3R-[2−14C,(5R)-5−3H1]mevalonic acid gave cholesterol with 3H/14C atomic ratio 6:5. 2. Conversion of the labelled cholesterol into 3β-acetoxy-6-nitrocholest-5-ene or cholest-4-ene-3,6-dione resulted in the loss of one tritium atom from C-6. 3. These results show that during cholesterol biosynthesis the 6α-hydrogen atom of a precursor sterol is eliminated during formation of the C-5–C-6 double bond. 4. Incorporation of 3R-[2−14C,(5R)-5−3H1]mevalonic acid into the sterols of larch (Larix decidua) leaves gave labelled cycloartenol and β-sitosterol with 3H/14C atomic ratios 6:6 and 6:5 respectively. 5. One tritium atom was lost from C-6 on conversion of the labelled β-sitosterol into either 3β-acetoxy-6-nitrostigmast-5-ene or stigmast-4-ene-3,6-dione, demonstrating that formation of the C-5–C-6 double bond of phytosterols also involves the elimination of the 6α-hydrogen atom of a precursor sterol. 6. The 3R-[2−14C,(5R)-5−3H1]mevalonic acid was also incorporated by larch (L. decidua) leaves into a sterol that co-chromatographed with 28-isofucosterol. Confirmation that the radioactivity was associated with 28-isofucosterol was obtained by co-crystallization with carrier 28-isofucosterol and ozonolysis of the acetate to give radioactively labelled 24-oxocholesteryl acetate. 7. The significance of these results to phytosterol biosynthesis is discussed.

scholarly journals The formation and reduction of the 14,15-double bond in cholesterol biosynthesis

1971 ◽  
Vol 121 (1) ◽  
pp. 131-137 ◽  
Author(s):  
I. A. Watkinson ◽  
D. C. Wilton ◽  
K. A. Munday ◽  
M. Akhtar
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Rat Liver ◽  
Related Compound ◽  
Cholesterol Biosynthesis ◽  
Liver Homogenate ◽  
Compound Iiia ◽  
Sterol Biosynthesis ◽  
Methyl Group

It was shown that 100μg quantities of 4,4′-dimethyl[2-3H2]cholesta-8,14-dien-3β-ol (IIIa), tritiated cholesta-8,14-dien-3β-ol, 4,4′-dimethyl[2-3H2]cholesta-7,14-dien-3β-ol, dihydro[2-3H2]lanosterol and [24-3H]lanosterol were converted by a 10000g supernatant of rat liver homogenate into cholesterol in 17%, 54%, 6%, 9.5% and 24% yields respectively. From an incubation of dihydro[3α-3H]lanosterol with a rat liver homogenate in the presence of a trap up to 38% of the radioactivity was found to be associated with a fraction that was unambiguously shown to be 4,4′-dimethylcholesta-8,14-dien-3β-ol. Another related compound, 4,4′-dimethylcholesta-7,14-dien-3β-ol was also shown to be equally effective in its ability to trap compound (IIIa) from an incubation of dihydro[3α-3H]lanosterol. The mechanism of the further conversion of the compound (IIIa) into cholesterol occurred by the reduction of the 14,15-double bond and involved the addition of a hydrogen atom from the medium to C-15 and another from the 4-position of NADPH to C-14. Two possible mechanisms for the removal of the 14α-methyl group in sterol biosynthesis are discussed.

scholarly journals The role of a cholesta-8,14-dien-3β-ol system in cholesterol biosynthesis

1969 ◽  
Vol 111 (5) ◽  
pp. 757-761 ◽  
Author(s):  
M. Akhtar ◽  
I. A. Watkinson ◽  
A. D. Rahimtula ◽  
D. C. Wilton ◽  
K. A. Munday
Keyword(s):  
Hydrogen Atom ◽  
Cholesterol Biosynthesis ◽  
Tritiated Water ◽  
Mevalonic Acid ◽  
Hydrogen Atoms ◽  
Steroid Biosynthesis ◽  
Methyl Group

The biosynthesis of cholesterol from squalene and tritiated water is described. Degradation of the cholesterol indicated that C-15 may be involved in cholesterol biosynthesis. In accordance with this view it is shown that in the conversion of [2RS−3H2]mevalonic acid into cholesterol one of the hydrogen atoms at C-15 is removed. A mechanism for the removal of the 14α-methyl group in steroid biosynthesis that involves the labilization of a C-15 hydrogen atom is outlined. In accordance with the requirement of this scheme it is shown that 4,4′-dimethyl-cholesta-8,14-dien-3β-ol is converted into cholesterol.

scholarly journals The incorporation of a hydrogen atom at C-15 of cholesterol biosynthesized from squalene

1969 ◽  
Vol 114 (4) ◽  
pp. 801-806 ◽  
Author(s):  
M Akhtar ◽  
A. D. Rahimtula ◽  
D. C. Wilton
Keyword(s):  
Hydrogen Atom ◽  
Cholesterol Biosynthesis ◽  
Tritiated Water ◽  
Total Radioactivity ◽  
Chemical Degradation

Cholesterol is biosynthesized from squalene in the presence of tritiated water. Chemical degradation reveals that a considerable percentage of the total radioactivity is present at C-15. This result confirms the previous observations on the involvement of a C-15 hydrogen atom in cholesterol biosynthesis.

The Effect of Oxidized Cholesterol on the Aorta of Rabbits- Scanning Electron Microscopic Observations

1982 ◽  
Vol 40 ◽  
pp. 340-341
Author(s):  
S. K. Pena ◽  
C. B. Taylor ◽  
J. Hill ◽  
J. Safarik
Keyword(s):  
Cholesterol Biosynthesis ◽  
Cholesterol Content ◽  
Arterial Injury ◽  
Electron Microscopic ◽  
Aortic Smooth Muscle ◽  
Oxidized Cholesterol ◽  
Initial Event ◽  
Membrane Structure And Function ◽  
Scanning Electron Microscopic ◽  
And Function

Introduction: Oxidized cholesterol derivatives have been demonstrated in various cell cultures to be very potent inhibitors of 3-hvdroxy-3- methylglutaryl Coenzyme A reductase which is a principle regulator of cholesterol biosynthesis in the cell. The cholesterol content in the cells exposed to oxidized cholesterol was found to be markedly decreased. In aortic smooth muscle cells, the potency of this effect was closely related to the cytotoxicity of each derivative. Furthermore, due to the similarity of their molecular structure to that of cholesterol, these oxidized cholesterol derivatives might insert themselves into the cell membrane, alter membrane structure and function and eventually cause cell death. Arterial injury has been shown to be the initial event of atherosclerosis.

Measurement of the Lamb shift in the hydrogen atom

1982 ◽  
Vol 138 (10) ◽  
pp. 347 ◽  
Author(s):  
Yurii L. Sokolov ◽  
V.P. Yakovlev
Keyword(s):  
Hydrogen Atom ◽  
Lamb Shift
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