The Stereochemistry of Hydrogen Transfer from NADPH Catalysed by 3‐Hydroxy‐3‐methylglutaryl‐coenzyme A Reductase from Rat Liver

Beedle, Alan S.; Munday, K. A.; Wilton, David C.

doi:10.1111/j.1432-1033.1972.tb01896.x

Cited by 28 publications

(9 citation statements)

References 16 publications

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“…However, it is of interest to compare this labelling with that of appropriate positions in malate and citrate (about 20 and 10 atoms%, respectively [27]) which are potential intermediates in the transfer of deuterium from NADH to NADPH. Since there is an isotope effect in the reduction of 3-hydroxymethyl-3-glutaryl coenzyme-A [28] the labelling of NADPH will be higher than the observed labelling of hydrogens in the cholesterol molecule. Thus, ethanol can serve as a significant source of hydrogens for cholesterol biosynthesis.…”

Section: Nadph Poolsmentioning

confidence: 86%

Utilization of the Carbon and Hydrogen Atoms of Ethanol in the Biosynthesis of Steroids and Bile Acids

Cronholm

Burlingame

Sjövall

1974

European Journal of Biochemistry

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[l-'H,]Ethanol, ethanol were administered to bile fistula rats under conditions ensuring a maximal rate of oxidation for about 24 h. Cholesterol, cholic acid, chenodeoxycholic acid and 3p, 1 lP,2l-trihydroxy-5a-pregnan-20-one were isolated from bile collected at intervals during the experiment. The fraction of molecules containing different numbers of heavy isotope atoms was measured by gas chromatography -mass spectrometry -computer techniques. The results were used to determine the origin of the cholesterol pools used as precursors for the different compounds isolated from bile.The bile acids were found to be formed from a cholesterol pool, the turnover of which was about 5 times more rapid than that of the cholesterol pool used for biliary excretion. The cholesterol pools used for biliary excretion and as corticosterone precursor seemed to be in equilibrium.The acetyl groups derived from ethanol were introduced into the steroids without exchange of hydrogens at C-2, and the acetyl-CoA pool used as precursor did not exchange with acetyl groups in e.g. citrate or fatty acids. A difference in incorporation of [2-'H3]acetyl groups and [l-13C]acetyl groups was interpreted to be due to an isotope effect. Ethanol contributed about 45% of the acetyl-CoA pool used as precursor of cholesterol and bile acids.Deuterium from [l-'H,]ethanol was incorporated in many positions of all the steroids. If it is assumed that the incorporation is mediated by NADPH, the deuterium excess of the hydrogens introduced was about 10 atoms %. The contribution via different pathways of an important part of the hydrogen and 'carbon atoms in cholesterol, bile acids and corticosteroids provides possible mechanisms by which ethanol may affect the biosynthesis and metabolism of steroids.

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Section: Nadph Poolsmentioning

confidence: 86%

Utilization of the Carbon and Hydrogen Atoms of Ethanol in the Biosynthesis of Steroids and Bile Acids

Cronholm

Burlingame

Sjövall

1974

European Journal of Biochemistry

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“…Both reductive steps from HMG-CoA to 4 involve hydride transfers from the 4-pro-R position (A side) of NADPH (8) 22,23 first to the thioester function resulting in the hemithioacetal mevaldyl-CoA (9) 24 and, after thiol elimination, to the aldehyde function of mevaldic acid (10, Scheme 3). An interesting stereochemical question is whether these reduction steps proceed by hydride addition to the Re or the Si faces of the thioester function in 4 and the aldehyde function in 10, respectively.…”

Section: The Stereochemical Course Of the Mevalonate Pathwaymentioning

confidence: 99%

Isoprenoids in three-dimensional space: the stereochemistry of terpene biosynthesis

Dickschat

2011

Nat. Prod. Rep.

110

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“…Further, little evidence has been reported on the reaction mechanism of the enzyme of animal origin [5,6].…”

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confidence: 99%

“…The hemithioacetal of mevaldate and CoA has been reported to be a good substrate of 3-hydroxy-3-methylglutaryl-CoA [5,6,20,21]. Since this compound, as well as mevaldate, has not been detected as a free intermediate in the reductase reaction, it is likely to exist in an enzyme-bound form.…”

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confidence: 99%

Kinetic Analysis of the Reaction Catalyzed by Rat‐Liver 3‐Hydroxy‐3‐methylglutaryl‐coenzyme‐A Reductase Using Two Specific Inhibitors

Tanzawa

Endo²

1979

European Journal of Biochemistry

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The mechanism of action of 3-hydroxy-3-methylglutaryl-CoA reductase solubilized from rat liver microsomes has been investigated. In the reduction of 3-hydroxy-3-methylglutaryl-CoA to mevalonate, an overall initial velocity study gave a linear intersecting pattern when both 3-hydroxy-3-methylglutaryl-CoA and NADPH were variable substrates. Adenosine 2'-monophospho-5'-diphosphoribose, which was found to be a reversible inhibitor of reductase, inhibited the enzyme competitively with respect to NADPH, and uncompetitively with respect to 3-hydroxy-3-methylglutaryl-CoA. On the other hand, the inhibition of reductase by ML-236B (sodium salt), a specific reversible inhibitor of the enzyme isolated from the culture of a Penicillium (whose structure is given in the paper) is competitive with respect to 3-hydroxy-3-methylglutaryl-CoA and noncompetitive with respect to NADPH FEBS Lett. 72, 323 -3261. The reduction of 3-hydroxy-3-methylglutaryl-CoA to mevalonate was subject to the substrate inhibition by NADPH attributed to the formation of a productive enzyme-NADPH complex. These results indicate that the two substrates bind to the enzyme effectively in an ordered manner; reductase first interacts with 3-hydroxy-3-methylglutarylCoA to make a binary complex, which, in turn, forms a ternary complex with one molecule of NADPH. Considered together with the results of product inhibition study, and assuming a hemithioacetal of mevaldate and CoA is an intermediate of the reductase reaction, a bi-uni-uni-ter-pingpong mechanism is proposed as a model of the overall reaction.3-Hydroxy-3-methylglutaryl-CoA reductase is an enzyme of current interest because of its regulatory role in cholesterogenesis [l, 21. The enzyme catalyzes the two-step reduction of 3-hydroxy-3-methylglutarylCoA to mevalonate in the presence of NADPH. 3-Hydroxy-3-methylglutaryl-Previous conclusions obtained from kinetic analyses with the reductase of bakers' yeast are contradictory [3,4]. Thus, Kirtley and Rudney first proposed a penta-uni-bi-ping-pong mechanism on the basis of an initial velocity pattern of parallel lines and product inhibition studies [3]. On the other hand, Qureshi et al. proposed a mechanism ordered throughout or random with respect to the binding of 3-hydroxy-3-methylglutaryl-CoA and the first molecule of NADPH by the analysis of the conversion of mevaldate to 3-hydroxy-3-methylglutaryl-CoA and mevalonate [4]. -.Ahhrroiation. CAMP, adenosine 3' : 5'-monophosphate. Enq-JrnP. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase or mevalonate: NADP oxidoreductase (EC 1.1.1.34).Further, little evidence has been reported on the reaction mechanism of the enzyme of animal origin [5,6].A previous report from this laboratory [7] has shown that the fungal metabolite ML-236B (Fig. 1) is a competitive inhibitor of the reductase. In the present experiments, binding characteristics of substrates to rat liver 3-hydroxy-3-methylglutaryl-CoA reductase was studied with the use of ML-236B and adenosine 2'-monophospho-5'-diphosphoribose, another potent inhibitor of ...

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The Stereochemistry of Hydrogen Transfer from NADPH Catalysed by 3‐Hydroxy‐3‐methylglutaryl‐coenzyme A Reductase from Rat Liver

Cited by 28 publications

References 16 publications

Utilization of the Carbon and Hydrogen Atoms of Ethanol in the Biosynthesis of Steroids and Bile Acids

Utilization of the Carbon and Hydrogen Atoms of Ethanol in the Biosynthesis of Steroids and Bile Acids

Isoprenoids in three-dimensional space: the stereochemistry of terpene biosynthesis

Kinetic Analysis of the Reaction Catalyzed by Rat‐Liver 3‐Hydroxy‐3‐methylglutaryl‐coenzyme‐A Reductase Using Two Specific Inhibitors

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