Alpha-methyl Group Research Articles

Further characterization of a Chinese hamster ovary cell mutant defective in lanosterol demethylation.

Sensitive in vitro lanosterol 14 alpha- and 4 alpha-methylsterol oxidase assays, particularly suitable for cell extracts of tissue culture cells, were developed and validated. Using these assays, we showed that the biochemical lesion of mutant 215, a cholesterol-requiring Chinese hamster ovary cell auxotroph isolated and partially characterized previously [Chang, T. Y., Telakowski, C., Vanden Heuvel, W., Alberts, A. W., & Vagelos, P. R. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 832-836], was localized at the 4 alpha-methylsterol oxidase enzyme system. The defect in 4 alpha-methylsterol oxidase activity in mutant 215 cells could be demonstrated by using either 4,4-dimethylcholestanol or 4 alpha-methylcholestanol as the substrate, suggesting that the enzyme systems responsible for 4 alpha-methyl- and 4,4-dimethylsterols may share a common component. However, demethylation of the C-14 alpha methyl group was found to occur at identical rates in wild-type and mutant 215, suggesting that C-14 alpha demethylation and C-4 alpha demethylation may occur by separate enzyme systems. A [3H]dihydrolanosterol incorporation experiment in intact cells of wild-type and mutant 215 supported these conclusions. Despite these results, a [14C]acetate pulse experiment indicated that [14C]lanosterol, instead of its 14C-labeled 14-demethylated sterol derivative(s), accumulated in intact cells of mutant 215. Possible implications of these findings for the mechanisms of lanosterol demethylation reactions are discussed.

Inhibition of sterol biosynthesis in animal cells by 14 alpha-hydroxymethyl sterols.

The chemical syntheses of a number of 14 alpha-hydroxymethyl sterols and 14 alpha -hydroxymethyl-15 alpha-hydroxysterols and their derivatives have been pursued to permit evaluation of their activity in the inhibition of sterol biosynthesis in animal cells in culture. Described herein are chemical syntheses of 7 alpha,8 slpha-epoxy-14 alpha-methyl-5 alpha-cholestan-3 beta,15 alpha-diol, 14 alpha-methyl-5 alpha-cholestan-3 beta,7 alpha,15 alpha-triol, 3 beta,15 alpha-diacetoxy-14 alpha-methyl-5 alpha-cholestan-7 alpha-ol, 3 beta,15 alpha-diacetoxy-7 alpha,32-epoxy-14 alpha-methyl-5 alpha-cholestane, 14 alpha-hydroxymethyl-5 alpha-cholest-6-en-3 beta,15 alpha-diol, 14 alpha-hydroxymethyl-5 alpha-cholest-7-en-3 beta,15 alpha-diol, 7 alpha,32-epoxy-14 alpha-methyl-5 alpha-cholestan-3 beta,15 alpha-diol, 14 alpha-hydroxymethyl-5 alpha-cholest-6-en-3-one, 14 alpha-hydroxymethyl-5 alpha-cholest-7-en-3-one, and 14 alpha-hydroxymethyl-5 alpha-cholets-7-en-15 alpha-ol-3-one. The effects of eight of the above compounds and of 14 alpha-hydroxymethyl-5 alpha-cholest-8-en-3 beta-ol, 14 alpha-hydroxymethyl-5 alpha-cholest-7-en-3 beta-ol, 14 alpha-hydroxymethyl-5 alpha-cholest-6-en-3 beta-ol, and 7 alpha,32-epoxy-14 alpha-methyl-5 alpha-cholestan-3 beta-ol on the synthesis of digitonin-precipitalbe sterols and on levels of HMG-CoA reductase activity in L cells and in primary cultures of fetal mouse liver cells have been investigated. All of the 14 alpha-hydroxymethyl sterols and 14 alpha-hydroxymethyl-15 alpha-hydroxysterols were found to be potent inhibitors of sterol synthesis and to reduce the levels of HMG-CoA reductase activity in these cells. Since hydroxylation of the 14 alpha-methyl group of 14 alpha-methyl sterol precursors of cholesterol can be considered as an obligatory step in the biosynthesis of cholesterol, the finding that 14 alpha-hydroxymethyl sterols are potent inhibitors of cholesterol biosynthesis and cause a reduction in the levels of HMG-CoA reductase activity raises the possibility that oxygenated sterol precursors of cholesterol, such as 14 alpha-hydroxymethyl sterols, may play an important role in the regulation of cholesterol synthesis and in the regulation of processes dependent upon mevalonate and sterol formation.

In vitro and in vivo effects of the antimycotic drug ketoconazole on sterol synthesis.

Ketoconazole, an orally active antimycotic drug, is a potent inhibitor of ergosterol biosynthesis in Candida albicans when added to culture media which support yeast or mycelial growth or to cultures containing outgrown mycelium. This inhibition coincides with accumulation of sterols with a methyl group at C-14 and can thus be attributed to an interference with one of the reactions involved in the removal of the 14 alpha-methyl group of lanosterol. When administered to rats infected with C. albicans, ketocanazole also inhibits fungal synthesis of ergosterol. A six-times-higher dose is required to effect cholesterol synthesis by rat liver.

Cell-free synthesis of a flavoprotein containing the 8 alpha-(N3-histidyl)-riboflavin linkage.

6-Hydroxy-D-nicotine oxidase is an inducible flavorprotein of Arthrobacter oxidans in which one mole of FAD is bound covalently to the polypeptide chain. During cell-free translation of polysomes from nicotine-induced A. oxidans cells in the presence of an Escherichia coli (MRE 600) supernatant fraction, labelled FAD, leucine and histidine were incorporated into 6-hydroxy-D-nicotine oxidase in the same ratio found in the enzyme isolated from whole cells. This indicates that one mole FAD is covalently attached per mol of 6-hydroxy-D-nicotine oxidase synthesized in vitro. In the native enzyme the coenzyme molecule is bound via its 8 alpha-methyl group to the N-3 atom of a histidyl residue. From the translation products an aminoacyl-riboflavin was isolated and its identity with synthetic 8 alpha-(N3-histidyl)-riboflavin was shown.

Therapy for urolithiasis by hydroxamic acids. II. Urease inhibitory potency and urinary excretion rate of hippurohydroxamic acid derivatives.

The apparent I50 values of various hippurohydroxamic acids against urease activity of sword bean were mostly 0.5 to 2.0 microM regardless of hydrophobicity of their substituents. However, the marked increase of hydrophilicity caused by substitution of trimethoxy groups conspicuously decreased the inhibitory potency. Methylation at alpha-position of the hydroxamic acid group in these compounds remarkably decreased the inhibitory potency, probably owing to steric hindrance by the alpha-methyl group. Thenoyl-, furoyl- and nicotino-glycinohydroxamic acids which are bioisostereomers of hippurohydroxamic acid had I50 values of 0.64, 1.3 and 5.3 microM, respectively. Furthermore, the inhibitory potency of some substituted hippurohydroxamic acids against the ureolytic activity of intact Proteus mirabilis isolated from patients with urinary tract infection, were half to one-tenth of those against urease activity of sword bean. On the other hand, m- and p-nitro-, m- and p-methoxy-, m- and p-acetylamino-hippurohydroxamic acid and furoylglycinohydroxamic acid showed high urinary excretion rates of 14 to 16% of the doses administered orally to rats, while most of the others had excretion rates of about 3 to 5%.

Studies on the mechanism of lanosterol 14 alpha-demethylation. A requirement for two distinct types of mixed-function-oxidase systems.

Carbon monoxide inhibited the removal of C-32 of dihydrolanosterol (I), but not of its metabolites 5 alpha-lanost-8-ene-3 beta,32-diol (II) and 3 beta-hydroxy-5 alpha-lanost-8-en-32-al (III). It appears therefore that cytochrome P-450 is a component of the enzyme system required to initiate oxidation of the 14 alpha-methyl group, but not of that responsible for the subsequent oxidation steps required for elimination of C-32 as formic acid. Non-radioactive compounds (II) and (III), when added to cell-free systems actively converting dihydrolanosterol into cholesterol, inhibited 14 alpha-demethylation measured by the rate of formation of labelled cholesterol from dihydro[1,7,15,22,26,30-14C]lanosterol or of labelled formic acid from dihydro[32-14C]lanosterol. However, neither compound (II) nor compound (III) accumulated radioactive label under these conditions. These observations could be attributed partly to inhibition of the initial oxidation of the 14 alpha-methyl group by compounds (II) and (III).

The antagonism by propranolol and alpha-methylpropranolol (ICI 77602) of vascular and cardiac responses to isoprenaline in anaesthetized dogs.

1. In anaesthetized dogs, alpha-methylpropranolol was less potent than propranolol in antagonizing both vascular (hind limb perfusion pressure) and cardiac heart rate) responses to isoprenaline. 2. alpha-Methylpropranolol was more potent in antagonizing vascular than cardiac responses to isoprenaline, but this selectivity was no greater than that seen also with propranolol. 3. Isoprenaline sensitivity was greater in the hind limb than the heart and vascular-selective antagonism was more pronounced in those dogs in which this differential sensitivity was the greatest. 4. Introduction of an alpha-methyl group into propranolol decreases its beta-adrenoceptor antagonist potency but does not enhance vascular selectivity.

GLUCOCORTICOID ACTIVITY OF VARIOUS PROGESTERONE ANALOGS: CORRELATION BETWEEN SPECIFIC BINDING IN THYMUS AND LIVER AND BIOLOGIC ACTIVITY*

When tested in an in vitro assay system, progesterone and various analogs of this steroid were shown to compete with [3H] triamcinolone acetonide (TA) for specific glucocorticoid receptors in both rat liver and thymus. Of these analogs, the following derivatives of progesterone were potent competitors of TA binding and, when injected into adrenalectomized rats, induced regression of the thymus and marked increases in hepatic tyrosine aminotransferase activity: 11 beta-hydroxyl, 6 alpha-methyl, 6 alpha, 16 alpha-dimethyl, and 6 alpha-methyl-17 alpha-hydroxyl. In contrast, progesterone, 16 alpha-methyl, and 17 alpha-hydroxy progesterone competed with TA in vitro but failed to elicit either gluco- or antiglucocorticoid activity in vivo. Also, we observed that the oral contraceptive 6 alpha-methyl-17-(1-propynyl)testosterone competes very effectively with TA in a cell-free preparation of rat liver and induces an increase in hepatic tyrosine aminotransferase activity. The 11 beta-hydroxyl group has previously been thought to be essential for glucocorticoid activity. Our studies indicate that substitution of progesterone or testosterone with a 6 alpha-methyl group negates the need for an 11 beta-hydroxyl substitutuent as a prerequisite for glucocorticoid activity.

ChemInform Abstract: ANALOGS OF BRADYKININ WITH RESTRICTED CONFORMATIONAL FREEDOM

Three analogs of bradykinin have been synthesized which bear an alpha-methyl group in the place of an alpha proton at position, 4, 5, or 8. Such analogs possess restricted conformational freedom and are of interest for three reasons. (1) They may provide information about the receptor-bound conformation of the peptide. (2) They may provide a route to antagonists of the native peptide. (3) They may be degraded slowly by proteolytic enzymes. None of the analogs described here antagonized the action of bradykinin, but one exhibited tissue specificity and decreased pulmonary inactivation in the rat.

ChemInform Abstract: CONFORMATIONAL ANALYSIS OF N‐NITROSOPIPERIDINES BY (13)C‐NMR, ORIENTATION PREFERENCE OF AN ALPHA‐METHYL GROUP

Chemischer InformationsdienstVolume 6, Issue 49 Physical Organic Chemistry ChemInform Abstract: CONFORMATIONAL ANALYSIS OF N-NITROSOPIPERIDINES BY (13)C-NMR, ORIENTATION PREFERENCE OF AN ALPHA-METHYL GROUP ROBERT R. FRASER, Search for more papers by this authorT. BRUCE GRINDLEY, Search for more papers by this author ROBERT R. FRASER, Search for more papers by this authorT. BRUCE GRINDLEY, Search for more papers by this author First published: December 9, 1975 https://doi.org/10.1002/chin.197549067Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue49December 9, 1975 RelatedInformation

Analogs of bradykinin with restricted conformational freedom.

Three analogs of bradykinin have been synthesized which bear an alpha-methyl group in the place of an alpha proton at position, 4, 5, or 8. Such analogs possess restricted conformational freedom and are of interest for three reasons. (1) They may provide information about the receptor-bound conformation of the peptide. (2) They may provide a route to antagonists of the native peptide. (3) They may be degraded slowly by proteolytic enzymes. None of the analogs described here antagonized the action of bradykinin, but one exhibited tissue specificity and decreased pulmonary inactivation in the rat.

Reactions of alpha methylene lactone tumor inhibitors with model biological nucelophiles.

Thiols are the most reactive nucleophilic reagents among the biological models investigated. They undergo "Michael-type" addition to the polyfunctional sesquiterpene lactones. The rapid rates of reaction with L-cysteine were measured and the reaction products were characterized. Each addition of thiol successively decreased the cytotoxicity of the adducts formed.

Inhibition of cholesterolgenesis in vitro by chlorophenoxyacetic acids. Effect of alpha-methyl groups.

Inhibition of cholesterolgenesis in vitro by chlorophenoxyacetic acids. Effect of alpha-methyl groups.

Enzymic oxidation of some alkylbenzenes in insects and vertebrates.

1. Oxidation rates of alkylbenzenes have been measured in 10000g supernatants of vertebrate livers, locust fat bodies and housefly abdomens. 2. Activity per g. of insect was greater in fly than locust preparations but both were of the same order as a range of vertebrate species. 3. Methyl groups of toluene and p-nitrotoluene were oxidized more rapidly than the side chains of higher homologues. 4. In the higher homologues hydroxylation occurred most readily at the alpha-methylene group and less readily at penultimate methylene and terminal methyl groups. 5. Oxidations in both vertebrates and insects were inhibited by piperonylbutoxide and similar synergists. 6. Oxidation activity was stimulated by pretreatment of rats, but not locusts, with phenobarbitone or 3,4-benzopyrene.

Electron Spin Resonance Spectroscopy: Application to Proof of Structure of Organic Ketones

Many ketones containing an alpha-methylene group can be converted to alpha-diketone radical anions in dimethyl sulfoxide solution. The resulting radical anions can usually be unambiguously identified by electron spin resonance spectroscopy, and the structure of the starting ketone may be deduced, often without reference to model compounds. The technique is also applicable to alpha-diketones, alpha-bromoketones, and alpha-hydroxyketones.

Biological activities of some 6-methylated progesterones.

A comparison of the progestational estrogen-antagonistic and adrenal depressant properties of a series of 6-methylated derivatives of progesterone is presented. Progestational activity was determined by a modified uterine carbonic anhydrase assay and the intrauterine assay of McGinty. Antagonism of estrone-induced uterine growth was determined in intact immature mice by mixing .3 mcg of estrone with spayed female rats by administrating the test compound for 14 days beginning 10 days after spaying. Introduction of a 6 alpha-methyl group into progesterone or 17 alpha-acetoxyprogesterone was generally accompanied by an increase in potency in each of the metrotropic assays. The exception was 6 alpha-methylprogesterone which showed a slight decrease in potency in the estrogen antagonism test. 3 compounds in which the configuration of the 6-methyl groups was planar revealed potencies the same as or slightly reduced from those of corresponding 6 alpha-methyl isomers. An exception was 6-methyl-6-dehydro-17-acetoxyprogesterone which had an oral potency 3 times that of the 6 alpha-methyl isomer. Its potency decreased on parenteral administration in the intrauterine and estrogen antagonism tests.

Free radicals in gamma-irradiated polystyrenes

Electron spin resonance spectra were observed for gamma irradiated polystyrene and for the substituted polystyrenes a-d/sub 1/, beta -d/sub 1/, p-d/ sub 1/. beta . beta -d/sub 2/, alpha , beta , beta -d/sub 3/, m-CH/sub 3/, alpha -CH/sub 3/, 2,5Cl/sub 2/, alpha , beta , beta -F/sub 3/, and 2, 3, 4, 5, 6-F/sub 5/. The spectra of al l the d-substituted styrenes irradiated at 77 K were nearly identical, consisting of three peaks with a separation of 37 gauss between center and end derivative peaks. The result is consistent with a radical structure formed by removal of alpha hydrogen and a major hyperfine interaction with the ontho ring hydrogens. The same structure seems to apply for gamma - irradiated pcly(m-methylstyrene) and poly( alpha beta beta trifluorostyrene). but in poly(2,5-dichlorostyrene) all hyperfine interactions are much lower. The radical from poly( alpha -methylstyrene) is formed by main-chain scission and shows evidence for relatively free rotation of the alpha methyl group. (auth)