Composition of essential oil of Zataria multiflora

The composition of the essential oil of Zataria multiflora Boiss. was studied by gas liquid chromatography (GLC), column chromatography (CC), NMR, and GLC/MS. The main constituents of the dry plant were thymol, carvacrol, while the main constituents of the fresh plant were thymol, carvacrol, p-cymene, linalool and gamma-terpinene. The structures of the major components were confirmed by IR and 1H-NMR.

Chemical and biological characterization of two FK506 analogs produced by targeted gene disruption in Streptomyces sp. MA6548

Two genetically engineered mutant strains of Streptomyces sp. MA6548 produced two FK506 analogs, 9-deoxo-31-O-demethylFK506 and 31-O-demethylFK506. The structures were determined by a combination of NMR and mass spectrometry. These compounds exhibited immunosuppressive and antifungal activities, albeit reduced, compared to FK506. Both compounds contain a free hydroxyl group at C-31 for the synthesis of novel FK506 derivatives.

Structural organization of a multifunctional polyketide synthase involved in the biosynthesis of the macrolide immunosuppressant FK506

The immunosuppressant FK506 is a 23-membered macrocyclic polyketide produced by several Streptomyces species. Sequencing of a 19.5-kb contiguous segment of DNA from the FK506 gene cluster of Streptomyces sp. MA6548 revealed the presence of a single 19.3-kb open reading frame designated fkbA. fkbA encodes a component of the FK506 polyketide synthase, a complex enzyme system which catalyzes synthesis of the polyketide portion of FK506. The predicted product of gene fkbA is a 630,660-Da protein (6420 amino acids) that contains 19 independent domains with a high degree of amino acid sequence similarity to the catalytic activities of known fatty acid synthases. The identified domains are arranged into four repeated modules with a linear organization precisely as that of animal fatty acid synthase and type I polyketide synthase. Each module participates in one round of chain extension and subsequent processing and thus FkbA polypeptide catalyzes four of the ten condensation steps required for synthesis of the FK506 macrolactone ring. Disruption of fkbA results in the generation of an FK506 non-producing mutant demonstrating direct involvement of fkbA in the biosynthesis of FK506.

Characterization of methyltransferase and hydroxylase genes involved in the biosynthesis of the immunosuppressants FK506 and FK520

FK506 and FK520 are 23-membered macrocyclic polyketides with potent immunosuppressive and antifungal activities. The gene encoding 31-O-demethyl-FK506 methyltransferase, fkbM, was isolated from Streptomyces sp. strains MA6858 and MA6548, two FK506 producers, and Streptomyces hygroscopicus subsp. ascomyceticus, an FK520 producer. The nucleotide sequence of the fkbM gene revealed an open reading frame encoding a polypeptide of 260 amino acids. Disruption of fkbM in Streptomyces sp. strain MA6548 yielded a mutant that produced 31-O-demethyl-FK506, confirming the involvement of the isolated genes in the biosynthesis of FK506 and FK520. Heterologous expression of fkbM in Streptomyces lividans established that fkbM encodes an O-methyltransferase catalyzing the methylation of the C-31 hydroxyl group of 31-O-demethyl-FK506 and FK520. A second open reading frame, fkbD, was found upstream of fkbM in all three aforementioned species and was predicted to encode a protein of 388 residues that showed a strong resemblance to cytochrome P-450 hydroxylases. Disruption of fkbD had a polar effect on the synthesis of the downstream fkbM gene product and resulted in the formation of 9-deoxo-31-O-demethyl-FK506. This established the product of fkbD as the cytochrome P-450 9-deoxo-FK506 hydroxylase, which is responsible for hydroxylation at position C-9 of the FK506 and FK520 macrolactone ring.

Microbial Demethylation of Immunosuppressant FK-506: Isolation of 31-O-FK-506-Specific Demethylase Showing Cytochrome P-450 Characteristics from Streptomyces rimosus MA187

As a result of an extensive screening program for the microbial modification of the immunosuppressant FK-506, one culture, Streptomyces rimosus MA187, which specifically catalyzed the C-31 demethylation of FK-506 was identified. Treatment of the biotransforming culture with FK-506 increased demethylase activity 2.4-fold and stabilized the cytochrome P-450 protein. The enzyme responsible for this demethylation (31-O-FK-506 demethylase) was isolated and shown to be a soluble cytoplasmic protein which is constitutively expressed in the cells, which requires NADPH, ferredoxin-NADP(sup+)-reductase, and ferredoxin for activity, and which shows a cytochrome P-450 light absorption characteristic. Carbon monoxide saturation of the enzyme preparation and known mammalian cytochrome P-450 inhibitors such as quinidine HCl, ketoconazole, troleandomycin, and sulfaphenazole abolish the demethylating activity extensively. The purified enzyme is a monomeric protein with a molecular mass of 42 kDa and shows its maximal activity at a pH of 7.4 and an incubation temperature of 34(deg)C. The first 19 N-terminal amino acids in the sequence of the purified protein have been determined, with no cytochrome P-450 match found in the OWL and Swiss-Prot 23 databases. The isolated demethylase is therefore a cytochrome P-450 protein that can be used as a catalyst for the synthesis of 31-O-desmethylFK-506, an important immunosuppressant and a known metabolite of FK-506 metabolism by human liver microsomes.

Integrative vectors for heterologous gene expression in Streptomyces spp

Integrative expression vectors for heterologous expression of the genes in Streptomyces were developed. The vectors are comprised of a strong constitutive promoter, PE, a synthetic ribosome-binding site, ATG start codon, multiple cloning site, transcription terminator and hygromycin-resistance-encoding gene. The vectors also contain a ColE1 replicon for propagation in Escherichia coli and a wide-host-range Streptomyces integration element, the mini-circle, to direct the insertion of the vectors into the Streptomyces genome at the mini-circle attachment site. HyR transformants are stable in the absence of drug selection. Conjugative derivatives were also constructed by incorporating oriT, the origin of transfer of the IncP plasmid RK2, into these vectors, and conjugal transfer was demonstrated from an appropriate E. coli donor to Steptomyces lividans (Sl). Derivatives of these vectors potentially useful for gene disruption, as well as complementation, are also described. Replicative forms of the constructed mini-circle-based vectors in Sl, that co-exist with the integrated copy of the vector, were also present without any apparent instability problems. The utility of the vectors was demonstrated by expression of the gene encoding 31-O-methyltransferase, which is involved in methylation at position 31 of the immunosuppressive drug FK506, in Sl.

Enzymology of FK-506 biosynthesis. Purification and characterization of 31-O-desmethylFK-506 O:methyltransferase from Streptomyces sp. MA6858

FK-506 is a macrolide antibiotic with immunosuppressant activity. Structurally, this compound contains three methylated hydroxyl groups at C13, C15 and C31. Previous biosynthetic studies using stable isotope-feeding experiments have established methionine as the source of the methyl for these methylated hydroxyl groups. Based on this information and also the availability of the 31-O-desmethylFK-506, a metabolic precursor for the biosynthesis of FK-506, a S-adenosyl-L-methionine-dependent enzyme assay was developed and the enzyme 31-O-desmethylFK-506 O:methyl-transferase was isolated from an extract of Streptomyces sp. MA 6858 and purified to near homogeneity. 31-O-DesmethylFK-506 O:methyltransferase is a monomeric protein with an apparent molecular mass of 30,000 Da and a pI of 4.4. The first 38 N-terminal amino acids have been sequenced and are H2N-SDVVETLRLPNGATVAHVNAGEAQFLYREIFTDRXYLRH. Functionally, This enzyme has a requirement for Mg2+ with an optimum temperature of 34 degrees C and a pH of 7.4 for full activity. Moreover, it catalyses the methylation of 31-O-desmethylimmunomycin as efficiently as its own natural substrate, 31-O-desmethylFK-506. Additionally, FKMT catalyzes the C31 transmethylation reaction of 13,31-O-bis-desmethyl-, 15,31-O-bisdesmethyl-, 13,15,31-O-trisdesmethyl- and 31-O-19,22-cyclic-hemiketalimmunomycins, which are all structural analogues of FK-506. The reaction is, however, completely blocked if the vicinal hydroxyl which is present at the C-32 position of the 31-O-desmethylFK-506 structure is replaced with azide, phosphate or other substituents. Finally, evidence is presented indicating the close similarity of FKMT and DIMT, a 31-O-desmethyl-immunomycin: O methyltransferase, previously isolated from a cell-free extract of Streptomyces hygroscopicus var ascomyceticus, an immunomycin (ascomycin/FK-520) producer.

Enzymatic synthesis and immunosuppressive activity of novel desmethylated immunomycins (ascomycins)

31-O-Desmethylimmunomycin O: methyltransferase (DIMT), an enzyme involved in the biosynthesis of immunomycin (ascomycin/FR-900520), was used to synthesize three analogs of this immunosuppressant compound. These compounds were assigned the following structures: 13-O-desmethyl-, 15-O-desmethyl- and 13,15-O-bisdesmethyl-immunomycins. Two of these compounds, namely, 15-O-desmethyl- and 13,15-O-bismethyl-immunomycins have novel structures and were examined for possible immunosuppressive activity by in vitro T-cell proliferation assay. The results showed that methylation of the C-15 hydroxyl is critical for full biological activity of the immunomycin.

Genetic relationships among actinomycetes that produce the immunosuppressant macrolides FK506, FK520/FK523 and rapamycin

A polyphasic taxonomic study was undertaken to establish the genetic and phenotypic relationships among six actinomycetes that produce the immunosuppressant macrolides FK506, FK520/FK523 and rapamycin. Chemotaxonomic studies reveal that all have Type I cell walls. Gas chromatography (GC) of fatty acid methyl esters revealed patterns consistent for strains of Streptomyces with 16:0 and 15:0 anteiso predominating. Principal component analysis of GC data revealed distinct profiles for each culture. Reciprocal DNA homology studies at Tm-25 showed the rapamycin-producing strain and one FK506-producing strain to have 38-50% homology with the type strain of Streptomyces hygroscopicus (ATCC 27438). The remaining strains exhibited 6-17% homology. To further explore the relationships among these strains all were probed for the presence of an O-methyltransferase gene specific to this biosynthetic pathway. Among the strains of interest, only Streptomyces hygroscopicus subsp. yakushimaensis, the patent strain for FK520/FK523, failed to hybridize with the probes.

Yeast FKBP-13 is a membrane-associated FK506-binding protein encoded by the nonessential gene FKB2

The immunosuppressants FK506 and rapamycin prevent T-cell activation and also inhibit the growth of certain strains of the yeast Saccharomyces cerevisiae. It has previously been shown that yeast contains a 12-kDa cytosolic FK506-binding protein (yFKBP-12), which also possesses peptidylprolyl cis-trans isomerase activity, and that fkb1 strains lacking yFKBP-12 are resistant to rapamycin and sensitive to FK506. The absence of yFKBP-12 permitted the detection and isolation of a second FK506- and rapamycin-binding protein, which is about 13 kDa in size (yFKBP-13) and membrane-associated. Purified yFKBP-13 binds FK506 with 15-fold lower affinity than yFKBP-12 and has peptidylprolyl cis-trans isomerase activity with a similar substrate profile. The sequence of the first 37 N-terminal amino acids was determined, and the yFKBP-13 gene (FKB2) was cloned and sequenced. A hydrophobic putative signal sequence precedes the N terminus of the mature protein. yFKBP-13 most closely resembles the membrane-associated human FKBP-13, which also possesses a signal peptide, whereas yFKBP-12 most closely resembles human FKBP-12. fkb2 and fkb1 fkb2 mutants are viable and unaltered in their sensitivity to FK506, suggesting that yeast possesses an additional target for this drug. Furthermore, fkb2 null mutations confer no change in rapamycin sensitivity. These findings show that yFKBP-13 and yFKBP-12 have distinct functions within the cell.

Long-acting contraceptive agents: testosterone esters of unsaturated acids

The synthesis of 13 new esters of testosterone is described, with the esterifying acids bearing acetylenic, olefinic, or polyunsaturated functions in the chain, for evaluation as long-acting androgens.

Disruption of a rhodaneselike gene results in cysteine auxotrophy in Saccharopolyspora erythraea

A 3,373-base-pair DNA segment from a clone fortuitously isolated from Saccharopolyspora erythraea by hybridization to an oligodeoxynucleotide probe was sequenced. Computer-assisted analysis of the nucleotide sequence reveals three closely linked Streptomyces open reading frames plus a fourth converging on the others. The deduced product of one of them, ORF2, shows considerable similarity to bovine liver rhodanese. orf2, and the closely linked orf3 located just downstream of it, were disrupted by insertion of an apramycin resistance cassette into the orf2 coding sequence along with inversion of the fragment carrying most of orf2 and orf3 via two successive recombinational events in the wild-type strain. The mutant strain thus created contains wild-type levels of rhodanese activity but cannot grow on minimal medium. It is a cysteine auxotroph, capable of utilizing efficiently only thiosulfate among the inorganic sulfur sources tested. orf2 has been designated cysA. The possible role of the rhodaneselike cysA gene product in thiosulfate formation is discussed.

Purification and reconstitution of the electron transport components for 6-deoxyerythronolide B hydroxylase, a cytochrome P-450 enzyme of macrolide antibiotic (erythromycin) biosynthesis

The hydroxylation of 6-deoxyerythronolide B (6D) to erythronolide B, a step in the biosynthesis of the 14-membered macrolide antibiotic erythromycin A by Saccharopolyspora erythraea, is catalyzed by a cytochrome P-450 monooxygenase that requires two electron transport proteins for the function of this terminal hydroxylase (A. Shafiee and C. R. Hutchinson, Biochemistry 26:6204-6210, 1987). Two flavoproteins and an iron-sulfur protein (erythrodoxin) were purified from S. erythraea CA340 and shown to act with 6D hydroxylase to catalyze the hydroxylation of (9R)-[9-3H]9-deoxo-9-hydroxy-6D in vitro in a suitably reconstituted system. The flavoproteins contained flavin adenine dinucleotide and exhibited characteristic absorption maxima at 356 and 456 nm. The one with an Mr of 47,000 showed NADPH-dependent diaphorase and cytochrome c reductase activity, and the other, with an Mr of 53,000 showed NADH-dependent activities of the same two types. Erythrodoxin contained acid-labile sulfur and iron, had an Mr of 27,500, and showed a broad absorption maximum between 394 and 404 nm. The sequence of its first 15 amino acids, except for position 12, was the same as that of the ferredoxin from Mycobacterium smegmatis.

Macrolide antibiotic biosynthesis: isolation and properties of two forms of 6-deoxyerythronolide B hydroxylase from Saccharopolyspora erythraea (Streptomyces erythreus)

A cytochrome P-450 monooxygenase that catalyzes the hydroxylation of 6-deoxyerythronolide B, an intermediate of erythromycin A biosynthesis in Saccharopolyspora erythraea (formerly Streptomyces erythreus), was resolved into two forms, P-450I and P-450II, by hydroxylapatite chromatography. These two proteins were purified to homogeneity from the CA 340 strain and found to have a P-450 content of 17.5 and 15.2 nmol/mg of protein, respectively. Either enzyme catalyzed the NADPH-dependent hydroxylation of 6-deoxyerythronolide B and (9R)- or (9S)-9-deoxo-9-hydroxy-6-deoxyerythronolide B in vitro when reconstituted with other electron-transport components from S. erythraea. Both of them had a Mr of 44,220 +/- 1350, a pI of 4.6, similar amino acid compositions, and an identical N-terminal sequence for the first five amino acids. They also showed identical antigenicity and cross-reactivity against polyvalent and specific antibodies and contained cytochrome P-450 in the low spin state with absorption maxima at 416, 532, and 565 nm. Their distinguishing characteristics were different activities toward the (9S)-9-deoxo-9-hydroxy-6-deoxyerythronolide B substrate and slightly different absorbance maxima in their dithionite-reduced CO-complexed spectra.

Potential long-acting contraceptive agents: esters of testosterone with alkoxy- and halogeno-substituted carboxylic acids

The chemical synthesis and physical data of several new esters of testosterone (17 beta-hydroxyandrost-4-en-3-one), which contain either a halogeno or an alkoxy substituent in the acid chain, are reported.

Oxidative demethylation of lanosterol in cholesterol biosynthesis: accumulation of sterol intermediates

With [3H-24,25]-dihydrolanosterol as substrate, large-scale metabolic formation of intermediates of lanosterol demethylation was carried out to identify all compounds in the metabolic process. Utilizing knowledge of electron transport of lanosterol demethylation, we interrupted the demethylation reaction allowing accumulation and confirmation of the structure of the oxygenated intermediates lanost-8-en-3 beta,32-diol and 3 beta-hydroxylanost-8-en-32-al, as well as the demethylation product 4,4-dimethyl-cholesta-8,14-dien-3 beta-ol. Further metabolism of the delta 8.14-diene intermediate to a single product 4,4-dimethyl-cholest-8-en-3 beta-ol occurs under interruption conditions in the presence of 0.5 mM CN-1. With authentic compounds, each intermediate has been rigorously characterized by high performance liquid chromatography and gas-liquid chromatography plus mass spectral analysis of isolated and derivatized sterols. Intermediates that accumulated in greater abundance were further characterized by ultraviolet, 1H-NMR, and infrared spectroscopy of the isolated sterols.

Potential long-acting contraceptive agents: esters and ethers of testosterone with alpha- and/or beta-chain branching

The synthesis of ten esters and two ethers of testosterone (17 beta-hydroxyandrost-4-en-3-one) is described. All these possess some form of alpha - and/or beta - substitution in the ester/ether side-chain. The work was undertaken in order to evaluate the long-acting antifertility effect of such compounds in males.

Cytochrome P-450-dependent oxidation of lanosterol in cholesterol biosynthesis. Microsomal electron transport and C-32 demethylation

Electron transfer to rat liver microsomal cytochrome P-450 of 14 alpha-methyl group demethylation of 24,25-dihydrolanosterol (C30-sterol) has been studied with a new radio-high-performance liquid chromatography assay. The monooxygenase is dependent upon NADPH plus oxygen, insensitive to CN-, and sensitive to CO. Microsomal oxidation is also sensitive to trypsin digestion, and reactivation is dependent upon the addition of purified, detergent-solubilized cytochrome P-450 reductase. Electron transport of C-32 sterol demethylation can be fully supported by very low concentrations of NADPH (approximately 10 microM) only in the presence of saturating concentrations of NADH (approximately 200 microM) suggesting involvement of cytochrome b5-dependent electron transfer in addition to the NADPH-supported pathway. The cytochrome P-450 of 14 alpha-demethylation has been solubilized with detergents, resolved chromatographically from cytochrome P-450 reductase and cytochrome b5, and fully active C-32 demethylase reconstituted. Incubation of intact microsomes with NADH and very low concentrations of NADPH described above leads to interruption of demethylation without 14 alpha-methyl group elimination. Under these conditions, C-32 oxidation products of the C30-sterol substrate accumulate at the expense of formation of demethylated, C29-sterol products. This enzymic interruption of C-32 demethylation, accumulation of oxygenated C30-sterols, along with subsequent demethylation of the isolated C30-oxysterols under similar oxidative conditions supports the suggestion that 14 alpha-hydroxymethyl and aldehydic sterols are metabolic intermediates of sterol 14 alpha-demethylation. Only very modest inductions of the constitutive cytochrome P-450 isozyme of 14 alpha-methyl sterol oxidase can be obtained with just 2 out of 12 known, potent inducers of mammalian hepatic cytochrome P-450s. Alternatively, administration of complete adjuvant in mineral oil drastically reduces amounts of total microsomal cytochrome P-450 while activity of 14 alpha-methyl sterol oxidase is not affected dramatically. Thus, as much as 2.5-fold enhancement of C-32 oxidase specific activity is obtained when expressed per unit of cytochrome P-450.

Microsomal enzymes of cholesterol biosynthesis from lanosterol. Characterization, solubilization, and partial purification of NADPH-dependent delta 8,14-steroid 14-reductase

The membrane-bound enzyme of microsomes that catalyzes NADPH-dependent reduction of the 14-double bond of conjugated delta 8,14- and delta 7,14-sterols has been studied both as collected in microsomes from broken cell preparations of rat liver and after solubilization. Optimal incubation conditions for assay of the membrane-bound enzyme have been determined, and properties of the microsomal enzyme have been established with respect to cofactor requirements, kinetics, pH, addition of inhibitors, addition of glycerol phosphatides, and sterol substrate specificity. The 14-reductase is readily solubilized with a mixture of octylglucoside and taurodeoxycholic acid. The solubilized enzyme has been enriched by precipitation with polyethylene glycol and chromatography on DEAE-Sephacel and hydroxylapatite columns. The resulting partially purified enzyme has been obtained free of other microsomal enzymes of cholesterol biosynthesis: 4-methyl sterol oxidase, delta 5,7-sterol 7-reductase, delta 8,24-sterol 24-reductase, 3-ketosteroid reductase, and steroid 8----7-ene isomerase, plus microsomal cytochrome P-450, cytochrome P-450 reductase, cytochrome b5 reductase, and cytochrome b5. The partially purified enzyme is stimulated by addition of phospholipids. All of the properties exhibited by partially purified 14-reductase are consistent with the suggestion that the solubilized and enriched enzyme catalyzes the microsomal reduction of the 14-double bond of the sterol-conjugated dienes. However, presence of the enzyme does not prove that the sterol-conjugated dienes are obligatory precursors of cholesterol.

delta 5,7,9(11)-Cholestatrien-3 beta-ol: a fluorescent cholesterol analogue

Structural analysis, a purification scheme and stability information on a fluorescent cholesterol analogue, which has been used as a probe in several model and biological systems, are presented. The proposed structure for the fluorophore, cholestatrien-3 beta-ol, closely resembles that of cholesterol. However, problems of low yield during synthesis and rapid decomposition have impeded its use. This study concerns the synthesis and purification of cholestatrien-3 beta-ol by reverse phase high performance liquid chromatography (HPLC). Unlike cholestatrien-3 beta-ol recrystallized from solvents, the fluorescent sterol purified by HPLC was stable over several months at -70 degrees C either as a white, crystalline powder or in ethanolic solution. In model membranes the fluorescence of cholestatrien-3 beta-ol was stable to ultraviolet (UV) light. A simple spectroscopic assay for purity is presented. Included are detailed absorbance, fluorescence, mass, 1H-NMR, and 13C-NMR spectral analyses. The data confirm the structure of cholestatrien-3 beta-ol proposed, but not proven, over 50 years ago, delta 5,7,9(11)-cholestatrien-3 beta-ol.

Long-acting contraceptive agents: norethisterone esters of arylcarboxylic acids

The synthesis of esters of norethisterone (17 alpha-ethynyl-17 beta-hydroxy-estr-4-en-3-one) with acids containing a benzene ring is described, two methods of esterification being compared in terms of yield and convenience. The activities of these esters as long-acting contraceptive agents have been evaluated.

Long-acting contraceptive agents: esters of norethisterone with alkoxy- and halogeno-substituted carboxylic acids

The chemical synthesis and physical data of several new esters of norethisterone (17 alpha-ethynyl-17 beta-hydroxyestr-4-en-3-one) are reported, which contain either a chloro- or an alkoxy-group as a substituent in the acid side-chain.

Long-acting contraceptive agents: cyclopropyl and cyclobutyl esters of norethisterone

Several esters of norethisterone (17 alpha-ethynyl-17 beta-hydroxyestr-4-en-3-one) with carboxylic acids containing a cyclopropyl or cyclobutyl ring have been synthesized and the stereochemistries of the side-chains determined.