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At least 109 records · Page 6Linked to original sources
PubMed1993

Biosynthesis and characterization of phosphatidylglycerophosphoglycerol, a possible intermediate in lipoteichoic acid biosynthesis in Streptococcus sanguis.

A membrane enzyme preparation from Streptococcus sanguis was shown to convert sn-[14C]glycerol 3-phosphate and CDP-diacylglycerol (or deoxyCDP-diacylglycerol) into a series of progressively higher-molecular-weight [14C]oligophosphoglycerophospholipids in vitro. The first oligophosphoglycerophospholipid to accumulate (termed lipid-1) was purified to homogeneity; chemical analysis, gas-liquid chromatography and chemical degradation studies indicated the most likely structure to be phosphatidylglycerophosphoglycerol (PGpG). PGpG is formed directly from two molecules of phosphatidylglycerol (PG), one molecule of PG serving as a sn-glycerol 1-phosphate (pG) donor and the second serving as the pG acceptor, with co-production of diacylglycerol. These oligophosphoglycerophospholipids may be intermediates in the biosynthesis of lipoteichoic acids.

Carbon Radioisotopes↗
PubMedDate not supplied

Effect of some sterol-biosynthesis-inhibiting fungicides on the biosynthesis of polyisoprenoid compounds in barley seedings.

The effect of five sterol-biosynthesis-inhibiting (SBI) fungicides, triadimefon, triarimol, diclobutrazol, tridemorph, and fenpropimorph on the germination, growth, and chloroplast pigment and sterol content of barley seedlings has been studied. Triadimefon, triarimol, and diclobutrazol at 250 microM depressed germination and growth, caused the accumulation of 14 alpha-methyl sterols, but had no effect on the formation of chlorophylls or carotenoids. Tridemorph and fenpropimorph at 250 microM had no effect on germination or the formation of chlorophylls and carotenoids but depressed growth and caused the accumulation of 9 beta,19-cyclopropyl sterols.

Carotenoids↗
PubMed1990

Hormonal regulation of complement biosynthesis in human cell lines--I. Androgens and gamma-interferon stimulate the biosynthesis and gene expression of C1 inhibitor in human cell lines U937 and HepG2.

C1 inhibitor (C1inh), a member of the serine protease inhibitor gene superfamily, is a glycosylated plasma protein inhibiting the proteolytic activities of C1r and C1s and involved in the regulation of coagulation, fibrinolysis and kinin-releasing systems. In this study, the in vitro effect of androgen hormones, dehydroepiandrosterone (DHEA), testosterone (TEST) and recombinant human gamma-interferon (gamma-IFN), has been determined on the production of C1inh in human cell lines. In both human monocytoid/histiocytoid cell line U937 and in hepatoma derived cell line HepG2, DHEA and TEST upregulated the gene expression and secretion of C1inh. The most pronounced effect was detected in the concn range 10(-7)-10(-9) M of the hormones. Under the same conditions DHEA and TEST had no detectable effect on the biosynthesis of C3, C2 and factor B by these cells, but DHEA at higher concn (10(-4) M) slightly increased that of C4 in HepG2 cells. Both in U937 and in HepG2 cells recombinant gamma-IFN markedly increased the gene expression and secretion of C1inh. This effect of gamma-IFN was abolished by histamine.

Carcinoma, Hepatocellular↗
PubMed1983

DNA and cholesterol biosynthesis in synchronized embryonic rat fibroblasts. I. Temporal relationships between HMG-CoA reductase activity, sterol biosynthesis and thymidine incorporation into DNA.

Temporal relationships between hydroxymethylglutaryl-CoA reductase activity, biosynthesis of C27 sterols, and [3H]thymidine incorporation into DNA were studied in a rat embryo fibroblast cell line synchronized by double thymidine block and cultured in cholesterol-containing medium. Cyclic variations of HMG-CoA reductase activity and C27 sterols occurred, with two maxima in S and G2M phases; the relative shortness of the G1 phase (3 h) in these cells could be responsible for the shift of sterol synthesis in the S phase. No noticeable variation of the individual C27 sterols was observed during the entire cell cycle. In each experiment, there was a good linear correlation between HMG-CoA reductase activity and C27 sterol synthesis, but from one experiment to another, a given level of enzymatic activity led to varying levels of [2-14C]acetate incorporation into sterols. In our experimental conditions, total HMG-CoA reductase activity is measured, and the preceding observation could be explained by a varying degree of phosphorylation of the enzyme depending on the metabolic state of the cells at the start of the experiment. The cyclic variations of the enzyme activity seem to be due more to increased synthesis at given times of the cycle than to periodic dephosphorylation. We question the existence of a relationship between cell division and cyclic sterol synthesis occurring in cells cultured in cholesterol-containing medium.

Acetates↗
PubMed1983

DNA and cholesterol biosynthesis in synchronized embryonic rat fibroblasts. II. Effects of sterol biosynthesis inhibitors on cell division.

The relationships between cholesterogenesis and cell division were studied by using two inhibitors of hydroxymethylglutaryl-CoA reductase activity--25-hydroxycholesterol and compactin. The effects of both compounds on DNA synthesis were compared in synchronized rat fibroblasts cultured in a cholesterol-containing medium. Compactin did not inhibit DNA synthesis, except after a long time of contact and at high and almost cytotoxic concentrations. 25-Hydroxycholesterol inhibited DNA synthesis (without cytotoxic effects) after only 9-16 h of contact, depending on the phase of the cell cycle at which this compound was added to the culture medium. Sensitivity of cells to 25-hydroxycholesterol was maximal at the end of the S phase/beginning of the G2M phase. The rapid effect of 25-hydroxycholesterol on DNA synthesis appears to be separate from the inhibitory effect on sterol or non-sterol mevalonate-derived compound synthesis. Indeed, under our experimental conditions, the suppression of cholesterol biosynthesis is compensated by the presence of cholesterol in the culture medium, as demonstrated by the lack of effect of compactin on DNA synthesis; moreover, addition of mevalonolactone to the culture medium did not reverse the effect of 25-hydroxycholesterol. 25-Hydroxycholesterol could inhibit DNA synthesis by a direct action on the nucleus, after transfer by the intermediary of a specific hydroxysterol-binding protein.

Acetates↗
PubMed1992

L-lysine repression of penicillin biosynthesis and the expression of penicillin biosynthesis genes acvA and ipnA in Aspergillus nidulans.

The addition of 0.1 M L-lysine to the fermentation medium reduced the production of penicillin by about 50% in Aspergillus nidulans. To analyse this effect at the molecular level, the expression of the penicillin biosynthesis genes acvA and ipnA, encoding delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase and isopenicillin N synthetase, was studied by using translational fusions with different reporter genes (strain AXB4A, acvA-uidA, ipnA-lacZ fusions; AXB4B, acvA-lacZ, ipnA-uidA fusions) integrated in single copy at the chromosomal argB locus of Aspergillus nidulans. Irrespective of the reporter genes used the expression of acvA and ipnA fusion genes was repressed in L-lysine grown cultures. The expression of a fusion gene of an A. nidulans primary metabolism gene (oliC-lacZ) was not affected by L-lysine.

2-Aminoadipic Acid↗
PubMed2005

Genes encoding enzymes responsible for biosynthesis of L-lyxose and attachment of eurekanate during avilamycin biosynthesis.

The oligosaccharide antibiotic avilamycin A is composed of a polyketide-derived dichloroisoeverninic acid moiety attached to a heptasaccharide chain consisting of six hexoses and one unusual pentose moiety. We describe the generation of mutant strains of the avilamycin producer defective in different sugar biosynthetic genes. Inactivation of two genes (aviD and aviE2) resulted in the breakdown of the avilamycin biosynthesis. In contrast, avilamycin production was not influenced in an aviP mutant. Inactivation of aviGT4 resulted in a mutant that accumulated a novel avilamycin derivative lacking the terminal eurekanate residue. Finally, AviE2 was expressed in Escherichia coli and the gene product was characterized biochemically. AviE2 was shown to convert UDP-D-glucuronic acid to UDP-D-xylose, indicating that the pentose residue of avilamycin A is derived from D-glucose and not from D-ribose. Here we report a UDP-D-glucuronic acid decarboxylase in actinomycetes.

Actinobacteria↗
PubMed1984

Biosynthesis of bufadienolides in toads. V. The origin of the cholesterol used by toad parotid glands for biosynthesis of bufadienolides.

Sodium (1-14C)acetate and (5-3H) mevalonate were incubated with Bufo arenarum toad parotid gland and liver tissues. Both labelled compounds were incorporated into cholesterol produced by liver while the incubations with parotid gland produced no labelled cholesterol. Low and high density lipoproteins isolated from toad plasma were iodinated and used for binding studies. Membrane preparations of parotid gland showed high affinity binding sites for 125I-LDL and 125I-HDL. In addition, while colchicine inhibits the in vitro uptake of (3H)cholesteryl linoleate-LDL into parotid gland tissue an opposite effect was seen with (3H)cholesteryl linoleate-HDL. The above mentioned results would support the hypothesis that the cholesterol used by the parotid gland for the biosynthesis of bufadienolides would be produced in the liver, transported by the circulating lipoproteins and incorporated by the glands by a receptor-mediated mechanism.

Animals↗
PubMedDate not supplied

Biosynthesis of acid mucopolysaccharides by the surviving new born rat skin. I. - Kinetics of the biosynthesis at the polymer level.

1) The amounts of individual mucopolysaccharides in the new born rat skin have been estimated and their specific rates of labelling assessed in vitro. Total and percentage amounts of these polymers agree satisfactorily with previously published data. 2) Relative rates of labelling from [U14C]-glucose have been estimated by combining column chromatography separation and electrophoresis on cellulose acetate strips. Specific radioactivities have been measured either with respect to the total uronic acid content of the fractions or with respect to their quantitative staining with Alcian Blue. The two methods agreed satisfactorily. 3) Average biosynthetic rates almost identical for hyaluronic acid and the total sulfated mucopolysaccharides. However, within the latter fraction, heparin + heparan sulfate incorporate [U14C]-glucose about 4 to 5 times more rapidly than the chondroitin sulfates. This result could not be expected from previous data obtained in vivo and is discussed with reference to a possible heterogeneity of the cell material whence the various mucopolysaccharides originate. 4) In the presence of puromycin, labelling of the sulfated mucopolysaccharides stops almost immediately, indicating a stringent requirement for protein primers. Biosynthesis of hyaluronic acid is affected only after preincubation of tissue with puromycin (one hour) and subsequent incubation of two hours with [U14C]-glucose.

Animals↗
PubMed2006

Methylglyoxal is an intermediate in the biosynthesis of 6-deoxy-5-ketofructose-1-phosphate: a precursor for aromatic amino acid biosynthesis in Methanocaldococcus jannaschii.

A biosynthetic pathway is proposed for creating 6-deoxy-5-ketofructose-1-phosphate (DKFP), a precursor sugar for aromatic amino acid biosynthesis in Methanocaldococcus jannaschii. First, two possible routes were investigated to determine if a modified, established biosynthetic pathway could be responsible for generating 6-deoxyhexoses in M. jannaschii. Both the nucleoside diphosphate mannose pathway and a pathway involving nucleoside diphosphate derivatives of fructose-1-P, fructose-2-P, or fructose-1,6-bisP were tested and eliminated. The established pathways did not produce the expected intermediates nor did the anticipated enzymes have the predicted enzymatic activities. Because neither anticipated pathway could produce DKFP, M. jannaschii glucose-6-P metabolism was studied in detail to establish exactly how glucose-6-P is converted into DKFP. This detailed analysis showed that methylglyoxal and a fructose-1-P- or fructose-1,6-bisP-derived dihydroxyacetone-P fragment are key intermediates in DKFP production. Glucose-6-P readily converts to fructose-6-P, which in turn converts to fructose-1,6-bisP. Fructose-6-P and fructose-1,6-bisP convert into glyceraldehyde-3-P (Ga-P-3), which converts into methylglyoxal by a 2,3-elimination of phosphate. The MJ1585-derived enzyme catalyzes the condensation of methylglyoxal with a dihydroxyacetone-P fragment, which is derived from fructose-1-P and/or fructose-1,6-bisP, generating DKFP. The elimination of phosphate from Ga-P-3 proceeds by both enzymatic and chemical routes in cell extracts, producing sufficient concentrations of methylglyoxal to support the reaction. This work is the first report of methylglyoxal functioning in central metabolism.

Fructosephosphates↗
PubMed2006

Halogenation of unactivated carbon centers in natural product biosynthesis: trichlorination of leucine during barbamide biosynthesis.

The in vitro reconstitution of leucine halogenation during barbamide biosynthesis has been accomplished. It has been demonstrated that the triple chlorination of the unactivated pro-R methyl group of the peptidyl carrier protein-tethered l-Leu substrate is carried out by the tandem action of two nonheme iron(II)-dependent halogenases, BarB1 and BarB2. Investigation of the substrate specificities of each of the halogenating enzymes revealed their complementary roles in the generation of trichloroleucine.

Cyanobacteria↗
PubMed2003

Biosynthesis of chloroplastidic and extrachloroplastidic terpenoids in liverwort cultured cells: 13C serine as a probe of terpene biosynthesis via mevalonate and non-mevalonate pathways.

Two terpenoid biosynthetic pathways, the mevalonate and non-mevalonate (glyceraldehyde phosphate-pyruvate) routes, were examined by feeding (13)C-labeled serines ([1-(13)C]- and [3-(13)C]-) to the cultured cells of the liverwort, Heteroscyphus planus. The labeling patterns observed in the isoprenoid unit of the biosynthetically (13)C-labeled stigmasterol corresponded to those expected from the mevalonate pathway, while those of the phytyl side chain corresponded to those from the non-mevalonate pathway. Thus, serine is a potential probe to determine the origin of terpenoid biosynthesis, in either the mevalonate or non-mevalonate pathway.

Acetylation↗
PubMedDate not supplied

Biosynthesis of antibiotics of the virginiamycin family, 5. The conversion of phenylalanine to phenylglycine in the biosynthesis of virginiamycin S1.

Conversion of L-phenylalanine to L-phenylglycine in the biosynthesis of virginiamycin S1 (1) can, in principle, take place with intramolecular nitrogen transfer or with intermolecular nitrogen transfer. A labeling experiment with DL-[3-13C, 15N]phenylalanine showed that the resulting L-phenylglycine contained no labeled nitrogen, indicating that the rearrangement proceeds via an intermolecular pathway.

Chemical Phenomena↗
PubMed1967

Studies on the biosynthesis of phenols in fungi. Biosynthesis of 3,4-dimethoxy-6-methyltoluquinol and gliorosein in Gliocladium roseum I.M.I. 93 065.

1. Gliorosein was obtained in excellent yield (150mg./200ml. of Raulin-Thom medium) from surface cultures of Gliocladium roseum. Its nuclear-magnetic-resonance spectrum showed conclusively that it is 1,6-dihydro-3,4-dimethoxy-6-methyltoluquinone. 2. Sodium [2-(14)C]acetate was incorporated into gliorosein and the related products (3.3% conversion). The specific activities of these substances increased in the order gliorosein, 3,4-dimethoxy-6-methyltoluquinol, the related quinhydrone and quinone, indicating that gliorosein was the actual metabolite that was secreted and that the other compounds were derived from it in the medium. 3. 6-Methylsalicylic acid was not taken up by the mycelium and could be recovered unchanged. Orsellinic acid was decarboxylated by G. roseum and an equivalent amount of orcinol was secreted into the medium. The methyl esters of 6-methylsalicylic acid and orsellinic acid were both hydrolysed by an esterase present in the mycelium. Some of the 6-methylsalicylic acid thus produced was secreted into the medium and the orsellinic acid was decarboxylated. 4. Washed mycelium of G. roseum converted aurantiogliocladin and 3,4-dimethoxy-6-methyltoluquinol quantitatively into gliorosein within 18hr. More critical experiments with (14)C-labelled substrates demonstrated that 3-hydroxy-4-methoxy-6-methyltoluquinol and 3,4-dimethoxy-6-methyltoluquinol, and their respective quinones, were effectively incorporated into gliorosein and related products (49, 68, 30 and 57% respectively). 5. The following sequence of reactions is proposed for the biosynthesis of gliorosein: acetyl-CoA+3 malonyl-CoA+S-adenosyl-methionine --> 5-methylorsellinic acid --> 3-hydroxy-4-methoxy-6-methyltoluquinol --> 3,4-dimethoxy-6-methyltoluquinol --> gliorosein. 6. Since gliorosein is optically active (dextrorotatory), the final tautomerization reaction leading to its formation must be enzyme-catalysed.

Acetates↗
PubMed1968

Biosynthesis of the pyrimidine moiety of thiamine. A new route of pyrimidine biosynthesis involving purine intermediates.

1. The pattern of distribution on the purine pathway of mutants of Salmonella typhimurium LT2 that had the double growth requirement for a purine plus the pyrimidine moiety of thiamine (ath mutants) indicated that purines and the pyrimidine moiety of thiamine share the early part of their biosynthetic pathways, and that 4-aminoimidazole ribonucleotide (AIR) is the last common intermediate. Two mutants that at first appeared anomalous were further investigated and found not to affect this deduction. 2. The ribonucleoside form of AIR (AIR(s)) satisfied the requirements both for a purine and for the pyrimidine moiety of thiamine of an ath mutant. 3. Methionine was required for the conversion of AIR into the pyrimidine moiety. 4. Radioactive AIR(s) was converted into radioactive pyrimidine moiety by an ath mutant without significant dilution of specific radioactivity. 5. Possible mechanisms for pyrimidine-moiety biosynthesis from AIR are discussed.

Autoradiography↗
PubMed1968

The biosynthesis of intestinal mucins. The effect of salicylate on glycoprotein biosynthesis by sheep colonic and human gastric mucosal tissues in vitro.

1. Incubation of sheep colonic mucosal scrapings in Krebs-Ringer buffer for 2(1/2)hr. in the presence of salicylate (15mm) resulted in decreased incorporation of radioactivity into the epithelial glycoprotein from the following labelled precursors: 16.6mum-d-[2-(14)C]glucose (83.9% inhibition), 20mum-l-[U-(14)C]threonine (82%) and (35)SO(4) (2-)(79%). Oxygen uptake measured simultaneously was diminished to 41% of the control value. 2. At lower concentrations of salicylate (e.g. 3.75mm), incorporation of 20mum-l-[U-(14)C]threonine was little affected (3-6% inhibition), whereas utilization of 4mum-d-[U-(14)C]glucose and (35)SO(4) (2-) was inhibited (41-48% and 40-59% of the control values respectively). 3. Analysis of the papain-digested glycoprotein from tissue incubations with 16.6mum-d-[2-(14)C]glucose in the presence of salicylate (3.75mm) showed large decreases in labelling of N-acetylneuraminic acid and N-glycollylneuraminic acid residues (57% and 34% of the control values respectively) and of hexosamine constituents (glucosamine, 55% inhibition; galactosamine, 33% inhibition). Labelling of neutral sugars (galactose and fucose) was relatively little affected (9 and 11% inhibition respectively). 4. Glucose 6-phosphate transaminase and glucosamine 6-phosphate acetylase in particle-free enzyme preparations of the sheep tissue were unaffected by salicylate at the above concentrations. Acetyl-CoA synthetase was markedly inhibited. 5. Human gastric mucosa (from operation), on incubation as above, had in one experiment an oxygen consumption of 9.9mul./hr./mg. dry wt. of tissue and incorporated 5mum-d-[U-(14)C]glucose (15.8% of the total radioactivity added) into bound hexosamine (20.6% of the total radioactivity incorporated), hexoses (glucose and galactose, 5.7%) and fucose (14.2%). The presence of salicylate (15mm) decreased the incorporation of 5mum-d-[U-(14)C]glucose into the glycoprotein by 74%, all sugar constituents being affected, without influence on the rate of oxygen consumption. 6. The results suggest an inhibitory effect of salicylate on glycoprotein biosynthesis at the level of the amino sugar intermediates.

Acyltransferases↗
PubMed1973

Biosynthesis of growth hormone in the rat anterior pituitary gland. Stimulation of biosynthesis in vitro by insulin.

The effect of insulin on the incorporation of radioactive leucine into growth hormone was investigated by using rat anterior pituitary glands incubated in vitro. A 50% stimulation over control values was observed at insulin concentrations above 2mum (280munits/ml). The effect was specific for growth hormone biosynthesis, over the range 1-5mum-insulin (140-700munits/ml). Lower more physiological concentrations had no significant effect in this system. Above 10mum (1.4 units/ml) total protein synthesis was also increased. The stimulation of growth hormone synthesis could be partially blocked by the addition of actinomycin D, suggesting that RNA synthesis was involved. Insulin was found to stimulate the rate of glucose utilization in a similar way to growth hormone synthesis. 2-Deoxyglucose and phloridzin, which both prevented insulin from stimulating glucose utilization, also prevented the effect of insulin on growth hormone synthesis. If glucose was replaced by fructose in the medium, the effect of insulin on growth hormone synthesis was decreased. We conclude that the rate of utilization of glucose may be an important step in mediating the effect of insulin on growth hormone synthesis.

Animals↗