Recent investigations on the nature of sterol intermediates in the biosynthesis of cholesterol

1972 ◽  
Vol 180 (1059) ◽  
pp. 125-146 ◽  
Keyword(s):  
Double Bond ◽  
Carbon Atom ◽  
Rat Liver ◽  
Liver Homogenate ◽  
Methyl Groups ◽  
Double Bonds ◽  
Animal Tissues ◽  
Methyl Group ◽  
Chromatographic Methods

Lanosterol(4,4,14α-trimethyl-cholesta-8,24-dien-3β-ol) has been proposed as the primary product of the cyclization of 2,3-epoxysqualene in animal tissues. Enzymic conversion of lanosterol to cholesterol requires reduction of the ∆ 24 double bond, removal of the three extra methyl groups, and shift of the nuclear double bond from ∆ 8 position to the ∆ 5 position. Until very recently, all of the proposed sterol intermediates in the biosynthesis of cholesterol possessed nuclear double bonds in the ∆ 8 , ∆ 7 , ∆ 5,7 or ∆ 5 positions. Consideration of possible mechanisms for the removal of the methyl group at carbon atom 14 of sterol precursors led to our demonstration of the presence of cholest-8(14)-en-3β-ol in animal tissues and establishment of the convertibility of this sterol to cholesterol in rat liver homogenate preparations. Reports (from other laboratories) of the stereospecific loss of the 15α-hydrogen of lanosterol upon enzymic conversion to cholesterol led to the demonstration of the convertibility of cholesta-8,14-dien-3β-ol, cholesta-7,14-dien-3β-ol, 14α-methyl-cholest-7-en-3β,15-diol, cholest-8(14)-en-3β,15α-diol, and cholest-8(14)-en-3β,15β-diol to cholesterol in rat liver preparations. We have recently developed chromatographic methods permitting the resolution of all of the C 27 sterols in question. The results of recent experiments directed towards an understanding of the detailed metabolism of these compounds are presented herein.

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.

Structural Homogeneity in Unsaturated Fatty Acids of Marine Lipids. A Review

1964 ◽  
Vol 21 (2) ◽  
pp. 247-254 ◽  
Author(s):  
R. G. Ackman
Keyword(s):  
Fatty Acids ◽  
Double Bond ◽  
Polyunsaturated Fatty Acids ◽  
Chain Length ◽  
Unsaturated Fatty Acids ◽  
Analytical Data ◽  
Double Bonds ◽  
Marine Origin ◽  
Methyl Group ◽  
Marine Lipids

Consideration of recent analytical data supports the conclusion that the longer-chain polyunsaturated fatty acids of marine origin are all structurally homogeneous in that the double bonds are cis, the double bonds methylene interrupted, and that, with the exception of the C16 chain length, the ultimate double bond will normally be three, six or nine carbon atoms removed from the terminal methyl group.

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.

THE ASSAY OF SUBCUTANEOUSLY INJECTED ANDROGENS IN THE CASTRATED RAT

1963 ◽  
Vol 42 (2) ◽  
pp. 245-253 ◽  
Author(s):  
Ralph I. Dorfman ◽  
Adeline S. Dorfman
Keyword(s):  
Double Bond ◽  
Levator Ani ◽  
Seminal Vesicles ◽  
Ventral Prostate ◽  
Methyl Groups ◽  
Albino Rat ◽  
Once Daily ◽  
Methyl Group ◽  
Assay Procedure ◽  
Androgenic Activity

ABSTRACT An assay procedure using the immature castrated albino rat is described using the weight of the seminal vesicles, ventral prostate, and levator ani as end-points in a ten day assay. The sensitivity was of the order of 0.6 mg of testosterone injected subcutaneously once daily in an aqueous suspending medium. The precision was adequate as judged by the λ values of 0.096 to 0.137 for the seminal vesicles, 0.128 to 0.162 for the ventral prostate, and 0.171 to 0.248 for the levator ani. Activity of testosterone was increased significantly by esterification, by introduction of the 17α-methyl group, and by reduction of the Δ4 double bond to the 5α form. Androgenic activity was decreased significantly by oxidation of the 17β-hydroxy group to the 17-keto group and introduction of methyl groups at the 2α- or 6α-positions.

scholarly journals Omega-3 as an Anti-Inflammatory Modality: Literature Review

2021 ◽  
Vol 7 (1) ◽  
pp. 141-147
Author(s):  
Rachmat Hidayat ◽  
Nur Riviati
Keyword(s):  
Fatty Acids ◽  
Double Bond ◽  
Carbon Atom ◽  
Growth And Development ◽  
Development Process ◽  
Vital Role ◽  
Omega 3 ◽  
Methyl Group ◽  
The Third ◽  
Fatty Acid Chain

A B S T R A C TOmega-3 fatty acids are polyunsaturated fatty acids that have multiple double bonds,the first double bond is located on the third carbon atom of the omega-methyl group,the next double bond is located at the third carbon atom from the previous doublebond. The methyl omega group is the last group in the fatty acid chain. Omega-3 fattyacids are nutrients that play a vital role in the growth and development process ofbrain neuron cells for the intelligence of the born baby.

scholarly journals Identification of the Tetrel Bonds between Halide Anions and Carbon Atom of Methyl Groups Using Electronic Criterion

Molecules ◽  
2019 ◽  
Vol 24 (6) ◽  
pp. 1083 ◽  
Author(s):  
Ekaterina Bartashevich ◽  
Yury Matveychuk ◽  
Vladimir Tsirelson
Keyword(s):  
Binding Energy ◽  
Carbon Atom ◽  
Molecular Complexes ◽  
Electron Donors ◽  
Methyl Groups ◽  
Geometrical Parameters ◽  
Halide Anion ◽  
Methyl Group ◽  
Electrophilic Site ◽  
Tetrel Bonds

The consideration of the disposition of minima of electron density and electrostatic potential along the line between non-covalently bound atoms in systems with Hal−···CH3–Y (Hal− = Cl, Br; Y = N, O) fragments allowed to prove that the carbon atom in methyl group serves as an electrophilic site provider. These interactions between halide anion and carbon in methyl group can be categorized as the typical tetrel bonds. Statistics of geometrical parameters for such tetrel bonds in CSD is analyzed. It is established that the binding energy in molecular complexes with tetrel bonds correlate with the potential acting on an electron in molecule (PAEM). The PAEM barriers for tetrel bonds show a similar behavior for both sets of complexes with Br− and Cl− electron donors.

scholarly journals The biological conversion of 7-dehydrocholesterol into cholesterol and comments on the reduction of double bonds

1968 ◽  
Vol 106 (4) ◽  
pp. 803-810 ◽  
Author(s):  
D. C. Wilton ◽  
K A Munday ◽  
S. J. M. Skinner ◽  
M Akhtar
Keyword(s):  
Hydrogen Atom ◽  
Rat Liver ◽  
Enzyme System ◽  
Tritiated Water ◽  
Liver Homogenate ◽  
Double Bonds ◽  
Hydrogen Atoms ◽  
Biological Conversion ◽  
Microsomal Pellet

It is shown that the 7-dehydrocholesterol reductase-catalysed conversion of 7-dehydrocholesterol into cholesterol (II), with a 105000g microsomal pellet of rat liver in the presence of [4−3H2]NADPH, results in the transfer of radioactivity to the 7α-position of cholesterol. When the conversion is carried out in the presence of tritiated water the label is introduced exclusively at the 8β-position. However, when the conversion of 7-dehydrocholesterol into cholesterol is performed with a 500g supernatant of rat liver homogenate the radioactivity is incorporated at both the 7α- and the 8β-position. Evidence is provided for the presence of an enzyme system in the 500g supernatant that catalyses an equilibration of hydrogen atoms between those at the 4-position of NADPH and those of water. The work with stereospecifically labelled cofactors shows that both the equilibrating system and the 7-dehydrocholesterol reductase utilize the 4B-hydrogen atom of NADPH. In the light of these results a mechanism for the reduction of carbon–carbon double bonds is discussed.

Folate status modulates the induction of hepatic glycine N-methyltransferase and homocysteine metabolism in diabetic rats

2006 ◽  
Vol 291 (6) ◽  
pp. E1235-E1242 ◽  
Author(s):  
Kristin M. Nieman ◽  
Cara S. Hartz ◽  
Sandra S. Szegedi ◽  
Timothy A. Garrow ◽  
Janet D. Sparks ◽  
...  
Keyword(s):  
Rat Liver ◽  
Folate Deficiency ◽  
Diabetic Rats ◽  
Carbon Pool ◽  
Diabetic Rat ◽  
Methyl Groups ◽  
Methyl Group ◽  
Diabetic State ◽  
Folate Status ◽  
Liver Folate

A diabetic state induces the activity and abundance of glycine N-methyltransferase (GNMT), a key protein in the regulation of folate, methyl group, and homocysteine metabolism. Because the folate-dependent one-carbon pool is a source of methyl groups and 5-methyltetrahydrofolate allosterically inhibits GNMT, the aim of this study was to determine whether folate status has an impact on the interaction between diabetes and methyl group metabolism. Rats were fed a diet containing deficient (0 ppm), adequate (2 ppm), or supplemental (8 ppm) folate for 30 days, after which diabetes was initiated in one-half of the rats by streptozotocin treatment. The activities of GNMT, phosphatidylethanolamine N-methyltransferase (PEMT), and betaine-homocysteine S-methyltransferase (BHMT) were increased about twofold in diabetic rat liver; folate deficiency resulted in the greatest elevation in GNMT activity. The abundance of GNMT protein and mRNA, as well as BHMT mRNA, was also elevated in diabetic rats. The marked hyperhomocysteinemia in folate-deficient rats was attenuated by streptozotocin, likely due in part to increased BHMT expression. These results indicate that a diabetic state profoundly modulates methyl group, choline, and homocysteine metabolism, and folate status may play a role in the extent of these alterations. Moreover, the upregulation of BHMT and PEMT may indicate an increased choline requirement in the diabetic rat.

scholarly journals Formation of malate from glyoxylate in animal tissues

1971 ◽  
Vol 121 (3) ◽  
pp. 447-452 ◽  
Author(s):  
Chi-Chin Liang ◽  
Lo-Chang Ou
Keyword(s):  
Rat Liver ◽  
Liver Homogenate ◽  
Animal Tissues

1. Incubation of rat liver homogenate with [1-14C]glyoxylate, ATP and acetate shows a rapid sequential incorporation of radioactivity into malate, oxaloacetate and citrate. 2. In liver from normal rats the rate of the formation of each substance in question is higher than that in liver from thiamin-deficient rats. 3. The net accumulation of malate is greater with liver from thiamin-deficient rats. Its further metabolism is retarded, it is suggested, by inhibitors formed by a condensation of glyoxylate and oxaloacetate.

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