Cholate inhibition

Although, as is well-known, cholate inhibits cytochrome oxidase (Wainio ct a/., 1948 Smith, 195Sa), it was used as a reagent for extraction or solubilization of cytochrome a from beef heart muscle (Yakushiji and Okunuki, 1940), because it is not known whether any detergents other than cholate or deoxycholate are effective for extraction of cytochrome a from these source materials. Therefore, it is very important to test the inhibition of activity in the cytochrome a preparation by cholate and to examine whether the activity lost during purification can be recovered by other types of detergents. It was found that Emasol 4130, a synthetic nonionic detergent, reactivated purified cytochrome a (Yonetani, 1959). 

Detergents (26, 41, 46, 96, 97) Optimal concentrations of deoxycholate, cholate, Triton X-100, and cetyltri-methylammonium bromide activate, as does urea. Activation of phosphotransferase > that of phosphohydrolase. Supraoptimal levels inhibit, as do all tested concentrations of sodium lauryl sulfate and Tweens 20 and 80. (See also Lysolecithin, Fatty acids, and Long-chain fatty acyl-CoA esters, above)... 

Phlorizin (7, 13, 16, 17, 89, 101, 146) Inhibits noncompetitively both phosphohydrolase and phosphotransferase activities inhibition of former potentiated by cetrimide and abolished or significantly ameliorated by deoxycholate, cholate, Triton X-100, or digitonin treatment of microsomes. Cetrimide reduces inhibition by phlorizin of phosphohydrolase... 

It has been shown by Ragan and Racker (36) that phospholipids are necessary for the ubiquinone, but not the ferricyanide, reductase activity of complex I. Thus, removal of about 50% of complex I lipids by extraction with cholate under special conditions resulted in a reversible loss of ubiquinone reductase activity without affecting the ferricyanide reductase activity. More phosphatidylcholine and phosphatidylethanolamine were removed by this procedure than cardiolipin. Readdition of either phosphatidylcholine or phosphatidylethanolamine restored considerable rotenone-sensitive ubiquinone-1 reductase activity, which was further augmented when small amounts of cardiolipin were also added. Using preparations depleted of ubiquinone-10 by pentane extraction, these authors have also shown that enzyme-bound ubiquinone-10 is not necessary for the reduction of added ubliquinone-1 by complex I or the inhibition of this reaction by rotenone. 

S. acidocaldarius (strain 7) contains a cyanide-sensitive cytochrome oxidase [24], The purified cytochrome (M, 150000) is composed of three subunits (M, 37000, 23 000, and 14000). Difference spectra following reduction with dithionite show a Soret band at 441 nm and a maximum at 603 nm characteristic of aa3-type cytochromes. In addition, there is a band at 558 nm whose connection to the oxidase is not clear. This oxidase is stimulated by cholate, but unlike the oxidase from the DSM 639 strain it is inhibited by low concentrations of cyanide (pM as opposed to mM) and oxidizes horse-heart cytochrome c, TMPD-ascorbate, and caldariella quinol. The rates of oxidation (pmol/min/mg protein) for cytochrome c, TMPD-ascorbate, and quinol are 63, 6.1, and 0.2, respectively. Another cytochrome oxidase that has an absorption maximum at 602 nm, oxidizes caldariella quinol, but does not oxidize cytochrome c, is also present in strain 7 so that the terminal portion of the electron transport system in S. acidocaldarius consists of at least three oxidases. It is suggested [8] that the presence of three oxidases in 5. acidocaldarius is unlikely and that the cyanide-sensitive oxidase was isolated from a different species, namely S. solfataricus. There is little taxonomic information in this assertion to judge whether strain 7 and DSM 639 are indeed different species. However, based on growth conditions reported by the investigators [12,28], which are unique for S. acidocaldarius and S. solfataricus [ 22, there is no reason to suspect that these organisms are different species. 

The isolation of an active, structurally intact complex was obtained using an association of cholate and octylglucoside and sucrose gradient centrifugation [111]. This preparation did not contain cytochrome 6-559 and possessed a plastoquinol-plastocyanine oxidoreductase activity, inhibited by specific inhibitors (DBMIB, UHDBT). The complex was essentially free of chlorophyll and contaminations by other membrane components, specifically of the ATPase complex. 

Choleretic agents stimulate the secretion of bile by the liver, thereby increasing the flow of bile. Examples include chenodeoxycholic acid, ursodeoxycholic acid and a semisynthetic cholate, dehydrocholic acid. Chenodeoxycholic acid appears to work by inhibiting HMG-CoA reductase. Dehydrocholic acid produces thin watery bile, so is used to flush small calculi out of the bile ducts, particularly after surgery. These agents are discussed in more detail in other articles see ANTIHYPERLIPIDAEMIC AGENTS CHOLERETIC AGENTS HMG-COA REDUCTASE INHIBITORS. 

THD-341 - The tricyclic diterpenold THD-341 (11), at an oral dose of 3 mg/kg or as 0.001% of the diet, lowered serum lipids in cholesterol-cholate fed rats. At a dietary level of 0.01%, THD-341 prevented aortic atheroma formation in cholesterol-fed rabbits and inhibited the progression of established lesions in rabbits fed the cholesterol diet. ... 

The participation of G proteins in ZP3 signaling was indicated initially by the inhibition of Ca mobilization (Florman etal., 1989,1992 Bailey etal., 1994) and of acrosome reactions (Endo et al., 1987, 1988) following treatment of intact sperm with pertussis toxin, and subsequently by the direct demonstration of G protein activation by ZP3 in digitonin/cholate-solubilized extracts of sperm (Ward et al., 1992 Wilde et al., 1992 Ward and Kopf, 1993). G, and G j are selectively activated by ZP3 and can account for the pertussis toxin-sensitivity of signaling pathway (Ward... 

The mechanism of the inhibition of the HMG-CoA reductase by bile adds shown in Fig. 14 is a matter of controversy. Weis and Dietschy did not observe any influence of taurocholate on cholesterol synthesis in bile fistula rats fed a cholesterol-free diet, and concluded that the inhibitory effect of bile acids on cholesterol synthesis may be related to the increased absorption of cholesterol by the presence of bile acids in the intestine [247]. However, Hamprecht et al. were able to demonstrate a reduction of HMG-CoA reductase activity in lymph fistula rats infused with cholate [248]. Results by Shefer et al. also indicate that bile acids inhibit HMG-CoA reductase directly [212]. It seems likely that the inhibitory effect of the bile acids on HMG-CoA reductase may involve both direct and indirect effects. It was recently established that the stimulation of HMG-CoA reductase activity in response to treatment with cholestyramine is associated with an increase of the specific mRNA [258]. 

This reaction in DMSO is much faster than that in water, and reaction of an anionic nucleophile in water should be inhibited by an anionic surfactant, e.g., sodium cholate. The evidence is consistent with formation of a complex between substrate and steroid, and it was suggested that the carboxylate group of the cholate ion could act as a nucleophile or general base. 

Neomycin is a polybasic, poorly absorbed antibiotic which forms insoluble precipitates with bile salts (99). It lowers serum cholesterol concentrations in man (100-102) and chickens (99) and increases fecal bile acid excretion. It inhibits the hepatotoxic effects of lithocholic acid ingestion in chickens (99) and prevents bacterial conversion of cholate to deoxycho-late (103). Neomycin, 6-12 g/day, induces a malabsorption syndrome, with mucosal changes similar to those of sprue (104). Bile salt metabolism is thus affected in at least three ways by neomycin (1) a binding effect similar to that of cholestyramine, (2) suppression of deconjugation and secondary bile formation caused by antimicrobial properties, and (3) possible impairment of absorption of bile salts by intestinal mucosa. The first probably accounts for most of the increased fecal excretion of bile salts. 

For 193 nm applications, evaluation of a series la) of cholate based dissolution inhibitors suggested that the dissolution inhibition of methacrylate-based resins by these derivatives is largely a function of the hydrophobicity of the cholates employed. The observed relative order of hydrophobicity and dissolution inhibition was lithocholate (1 pendant hydroxyl) > deoxycholate == ursocholate (2 pendant hydroxyls) > cholate (3 pendant hydroxyls). Experiments using monomeric dissolution inhibitors such as t-butyl cholate (la), t-butyl deoxycholate (lb), t-butyl lithocholate (Ic), t-butyl lithocholate acetate (2) with the P(NB/MA) acrylate resins afforded resist systems that exhibited low contrast, poor adhesion, dark erosion (unexposed resist film loss) and were incompatible with industry standard 0.26 N TMAH developers. 

Some properties of the poly(ADP-ribose) synthetase activity associated with the M-R fraction are summarized in Table 3. The activity is strongly inhibited by nicotinamide, thymidine, theophylline, and 3-aminobenzamide. As discussed before, sodium deoxy-cholate is also inhibitory. 

ATP inhibit nonspecific nucleotidases. Another way to prepare [a P] GTP Arfl for the GAP assay is to incubate Arfl with 25 ruM HEPES, pH 7.4, 100 mM NaCl, 3.5 mM MgCl2, 1 mM EDTA, 1 mM ATP, 1 fjM [a PJGTP (specific activity = 50,000-250,000 cpm/pmol), 25 ruM KCl, 1.25 U/ml pyruvate kinase, and 3 mM phosphoenolpyruvate. This buffer contains a GTP regenerating system. If using Arfl that has not been myristoy-lated, include 0.1% (w/v) Triton X-100. For myristoylated Arfl, use either micelles of 3 mM dimyristoylphosphatidylcholine and 0.1% cholate, pH 7.4 or use vesicles prepared by extrusion or sonication (see Chapter 15 of this volume. Assay and Properties of the Arf GAPs AGAPl, ASAPl, and ArfGAPl). 

Cholestyramine resin in the form of glycocholate or taurocholate salts did not inhibit cholesterol rise in plasma in cholesterol-fed cockerels (22), presumably because these forms of resin were already saturated with bile acids and could not take up more. The stearate salts of cholestyramine resins, however, were fully active. The therapeutic effectiveness of the resin depends on the selectivity between the bile salt anions and the chloride anion as well as the capacity for the organic ion. Studies have therefore been made (18, 19) to determine the separation factors for these ions on various resins in order to investigate some of the properties of the resin that are responsible for the high affinity of the large organic ions for the ion-exchange resins. Since the number of equivalents of cholate anion bound were equal to the number of equivalents of chloride ion released by the resin, within the limits... 

The effects of individual bile salts on the hydrolysis of Cibachron Blue starch by a-amylase at pH 6.0 have been studied. Measurements with cholate, deoxy-, tauro-, taurodeoxy-, taurochenodeoxy-, chenodeoxy-, and lithio-cholates demonstrated that these salts can either inhibit or enhance the a-amylase activity. Since the pH of the jejunum is [Pg.356]

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