[Preparation of panax notoginseng saponins-tanshinone H(A) composite method for pulmonary delivery with spray-drying method and its characterization]

OBJECTIVE

To prepare panax notoginseng saponins-tanshinone II(A) composite particles for pulmonary delivery, in order to explore a dry powder particle preparation method ensuring synchronized arrival of multiple components of traditional Chinese medicine compounds at absorption sites.

METHOD

Panax notoginseng saponins-tanshinone II(A) composite particles were prepared with spray-drying method, and characterized by scanning electron microscopy (SEM), confocal laser scanning microscope (CLSM), X-ray diffraction (XRD), infrared analysis (IR), dry laser particle size analysis, high performance liquid chromatography (HPLC) and the aerodynamic behavior was evaluated by a Next Generation Impactor (NGI).

RESULT

The dry powder particles produced had narrow particle size distribution range and good aerodynamic behavior, and could realize synchronized administration of multiple components.

CONCLUSION

The spray-drying method is used to combine traditional Chinese medicine components with different physical and chemical properties in the same particle, and product into traditional Chinese medicine compound particles in line with the requirements for pulmonary delivery.

[Cloning and induced expression analysis of 4-hydroxy-3-methyl-but-2-enyl diphosphate reductase gene (smHDR) of Salvia miltiorrhiza]

This study reported the obtainment of the full-length cDNA of Salvia miltiorrhiza hairy roots (Abbr: SmHDR, GenBank number: JX233817), via extracting Salvia miltiorrhiza hairy roots total RNA, designing specific primers according to the transcriptome data and using the RACE strategy, and then analyzed it with bioinformatics approaches. On this basis, using the real-time PCR to detect SmHDR gene expression after Ag+ induction, and testing tanshinones contents of corresponding samples by UPLC. SmHDR has 1 647 nucleotides, and an open reading frame (ORF) encoding a protein of 463 amino acid residues. The deduced protein has isoelectric point (pI) of 5.72 and a calculated molecular weight about 51.88 kD. In the secondary structure, the percentage of alpha helix, beta turn and random coil were 35.64%, 20.30% and 44.06%, respectively. Sequence alignment and phylogenetic analysis demonstrated that SmHDR had relative close relationship to the HDR of Picrorhiza kurrooa, similar to HDR from other species of plants. Real time PCR results indicated that elicitor of Ag+ stimulated the increase of mRNA expression of SmHDR. At the same time, results of ultra performance liquid chromatography (UPLC), used to examine the accumulation of diterpenoid tanshinones in hairy roots, showed that the contents of diterpenoid tanshinones in hairy roots of Salvia miltiorrhiza were increased dramatically at 12 h after treated with Ag+, and then decreased significantly. This result showed a positive correlation between the levels of mRNA expression and tanshinones accumulation in Salvia miltiorrhiza stimulated by Ag+. The content of tanshinones was gradually raised, and it had an obvious increase at 120 h. The bioinformatics analysis and gene expression indicated that SmHDR might be involved in tanshinones biosynthesis, which laid the foundation for further study of secondary metabolic regulation mechanism of tanshinones.

Ultrasound-assisted extraction of carnosic acid and rosmarinic acid using ionic liquid solution from Rosmarinus officinalis

Ionic liquid based, ultrasound-assisted extraction was successfully applied to the extraction of phenolcarboxylic acids, carnosic acid and rosmarinic acid, from Rosmarinus officinalis. Eight ionic liquids, with different cations and anions, were investigated in this work and [C(8)mim]Br was selected as the optimal solvent. Ultrasound extraction parameters, including soaking time, solid-liquid ratio, ultrasound power and time, and the number of extraction cycles, were discussed by single factor experiments and the main influence factors were optimized by response surface methodology. The proposed approach was demonstrated as having higher efficiency, shorter extraction time and as a new alternative for the extraction of carnosic acid and rosmarinic acid from R. officinalis compared with traditional reference extraction methods. Ionic liquids are considered to be green solvents, in the ultrasound-assisted extraction of key chemicals from medicinal plants, and show great potential.

Metabolic profiles and cDNA-AFLP analysis of Salvia miltiorrhiza and Salvia castanea Diel f. tomentosa Stib

Plants of the genus Salvia produce various types of phenolic compounds and tanshinones which are effective for treatment of coronary heart disease. Salvia miltiorrhiza and S. castanea Diels f. tomentosa Stib are two important members of the genus. In this study, metabolic profiles and cDNA-AFLP analysis of four samples were employed to identify novel genes potentially involved in phenolic compounds and tanshinones biosynthesis, including the red roots from the two species and two tanshinone-free roots from S. miltiorrhiza. The results showed that the red roots of S. castanea Diels f. tomentosa Stib produced high contents of rosmarinic acid (21.77 mg/g) and tanshinone IIA (12.60 mg/g), but low content of salvianolic acid B (1.45 mg/g). The red roots of S. miltiorrhiza produced high content of salvianolic acid B (18.69 mg/g), while tanshinones accumulation in this sample was much less than that in S. castanea Diels f. tomentosa Stib. Tanshinones were not detected in the two tanshinone-free samples, which produced high contents of phenolic compounds. A cDNA-AFLP analysis with 128 primer pairs revealed that 2300 transcript derived fragments (TDFs) were differentially expressed among the four samples. About 323 TDFs were sequenced, of which 78 TDFs were annotated with known functions through BLASTX searching the Genbank database and 14 annotated TDFs were assigned into secondary metabolic pathways through searching the KEGGPATHWAY database. The quantitative real-time PCR analysis indicated that the expression of 9 TDFs was positively correlated with accumulation of phenolic compounds and tanshinones. These TDFs additionally showed coordinated transcriptional response with 6 previously-identified genes involved in biosynthesis of tanshinones and phenolic compounds in S. miltiorrhiza hairy roots treated with yeast extract. The sequence data in the present work not only provided us candidate genes involved in phenolic compounds and tanshinones biosynthesis but also gave us further insight into secondary metabolism in Salvia.

Differential patterns of dehydroabietic acid biotransformation by Nicotiana tabacum and Catharanthus roseus cells

The aim of this study was to use whole cell catalysts as tools for modification of selected resin acids in order to obtain value-added functional derivatives. The enzymatic bioconversion capacities of two plant species were tested towards dehydroabietic acid. Dehydroabietic acid (DHA) is an abundant resin acid in conifers, representing a natural wood protectant. It is also one of the constituents found in by-products of the kraft chemical pulping industry. DHA was fed to tobacco (Nicotiana tabacum) and Madagascar periwinkle (Catharanthus roseus) plant cell and tissue cultures and bioconversion product formation was monitored using NMR analysis. Both plant species took up DHA from culture medium, and various types of typical detoxification processes occurred in both cultures. In addition, diverse responses to DHA treatment were observed, including differences in uptake kinetics, chemical modification of added substrate and changes in overall metabolism of the cells. Interestingly, Catharanthus roseus, a host species for pharmaceutically valuable terpenoid indole alkaloids, exhibited a very different bioconversion pattern for exogenously applied DHA than tobacco, which does not possess a terpenoid indole pathway. In tobacco, DHA is readily glycosylated in the carbonyl group, whereas in periwinkle it is proposed that a cytochrome P450-catalyzed enzymatic detoxification reaction takes place before the formation of glycosylated product.

[Correlation between expression level of functional genes and tanshinones' accumulation in Salvia miltiorrhiza from different areas]

OBJECTIVE

To study the relationship between functional gene expression in Salvia miltiorrhiza from different producing areas and active principles, which might provide scientific basis for the gene regulation of tanshinones.

METHOD

The quantitative determination of cryptotanshinone and tanshinone II A was carried out by using HPLC method, expression level of 3 functional genes of SmAACT, SmCMK and SmIPPI were investigated by real-time PCR method.

RESULT

The content of active principles together with expression level of SmAACT and SmCMK were higher in S. miltiorrhiza from genuine producing areas including Henan and Shanxi, but lower in samples from Beijing which was non-genuine producing area.

CONCLUSION

Expression level of SmAACT and SmCMK had close relationships involving tanshinones' accumulation, but the SmIPPI gene had not.

Kinetin applications alleviate salt stress and improve the antioxidant composition of leaf extracts in Salvia officinalis

A pot experiment was carried out under glasshouse conditions with common sage (Salvia officinalis L.) to investigate the interactive effects of salt stress and kinetin on growth attributes and the abundance of pigments, ions, phenolic diterpenes and α-tocopherol in leaf extracts of this species. The plants were subjected to the following four treatments: (i) control (nutrient solution), (ii) control + 10 μM kinetin, (iii) salt stress (nutrient solution + 100 mM NaCl), and (iv) salt stress + 10 μM kinetin. Kinetin was applied as a foliar fertilizer. Salt stress reduced water contents, photosynthetic activity and pigment contents of sage leaves. In addition, it increased Na(+) contents, and reduced those of Ca(2+) and K(+) in leaves. Salt stress reduced carnosic acid and 12-O-methyl carnosic acid contents in leaves, while it did not affect carnosol and α-tocopherol contents. Foliar applications of kinetin seemed to counterbalance or alleviate the stress symptoms induced by salinity, improving ion and pigment contents, while leaf phenolic diterpene (mainly carnosol) and α-tocopherol contents also increased in both control and NaCl-treated plants; still this effect was much more obvious in salt-treated plants. A similar effect was also obtained when plants were sprayed with KNO(3) or Ca(NO(3))(2), thus suggesting that kinetin effects were at least partly due to an improvement of ion homeostasis. Kinetin applications resulted in increased transcript levels of the isoprenoid and tocopherol biosynthetic genes, DXPRI and VTE2 and VTE4 in control plants, but not in NaCl-treated plants. We conclude that kinetin can alleviate the negative impact of salt on sage plants cultivated under arid environments with salinity problems.

[Effects of elicitors on accumulation of phenolic acids and tanshinones in Salvia miltiorrhiza hairy root]

OBJECTIVE

To observe the effects of a biotic elicitor fungal hyphae extract, an abiotic elicitor methyl jasmonate and their synergistic action on the accumulation of phenolic acids and tanshinones in Salvia miltiorrhiza hairy root.

METHOD

Different elicitors were added to S. miltiorrhiza hairy root, which was subcultured for 21 days, the dry weight and contents of phenolic acids and tanshinones were determined at different harvest-time.

RESULT

S. miltiorrhiza hairy root growth was significantly inhibited by all three treatments and the accumulation of cryptotanshinone and dihydrotanshinone were promoted by each elicition. As for the accumulation of phenolic acids, there were differences between fungal elicitor and methyl jasmonate treatments, they were promoted by methyl jasmonate while inhibited in a certain extent by fungal hyphae extract.

CONCLUSION

Fungal elicitor, methyl jasmonate and their synergistic action have significant influence on accumulation of components in S. miltiorrhiza hairy root, and the effect varies between phenolic acids and tanshinones. There is no correlation between production of water-soluble ingredients and fat-soluble components on the whole under three different treatments.

Influence of ionic interactions on essential oil and phenolic diterpene composition of Dalmatian sage (Salvia officinalis L.)

The potential of four essential cations (K(+), Ca(2+), Mg(2+) and Fe(2+)) to alleviate salt toxicity was studied in sage (Salvia officinalis L.) plants grown in pots. Two concentrations of the following chloride salts: KCl, CaCl₂, MgCl₂ and FeCl₃, were used together with 100mM NaCl to study the effects of these nutrients on plant growth, leaf essential oils (EOs) and phenolic diterpenes composition. The sage plants accumulated Na(+) in their leaves (includers); this has affected secondary metabolites' biosynthesis. Treatment with 100mM NaCl slightly decreased borneol and viridiflorol, while increased manool concentrations. Addition of KCl, CaCl₂ and MgCl₂ increased considerably in a dose-dependent manner the oxygen-containing monoterpenes (1.8-cineole, camphor, β-thujone and borneol) in 100mM NaCl-treated sage. Whereas, the contents of viridiflorol decreased further with the addition of KCl in 100mM NaCl-treated sage. Our results suggest that the changes in EOs composition were more related to K(+) and Ca(2+) availability than to Na(+) toxicity. Furthermore, treatment with NaCl decreased by 50% carnosic acid (CA), a potent antioxidant, content in the leaves. K(+) and Ca(2+) promoted the accumulation of CA and its methoxylated form (MCA) in the leaves. The concentration of CA was positively correlated with leaf K(+) (r=0.56, P=0.01) and Ca(2+) (r=0.44, P=0.05) contents. It appears that different salt applications in combination with NaCl treatments had a profound effect on EOs and phenolic diterpene composition in sage. Therefore, ionic interactions may be carefully considered in the cultivation of this species to get the desired concentrations of these secondary metabolites in leaf extracts.

Testing and enhancing the in vitro bioaccessibility and bioavailability of Rosmarinus officinalis extracts with a high level of antioxidant abietanes

An antioxidant-enriched extract (RE) was obtained from rosemary (Rosmarinus officinalis) by supercritical fluid extraction to be used as an ingredient to design functional foods. The optimized mixture (42 mg RE g(-1) sunflower oil) was submitted to in vitro digestion and absorption tests (using Caco2 cells) to investigate the effect of these processes on its DPPH scavenging activity and also whether its major abietanes (tricyclic diterpenes) might be bioaccessible and bioavailable. Results indicated that supplementation of the rosemary extract with sunflower oil and lecithin (37 mg g(-1)) enhanced abietanes micellation (almost 2-fold). In vitro digestion of the mixture including RE, sunflower oil, and lecithin reduced 50% the bioaccesibility in terms of antioxidant activity. Bioavailability was 31%. It was evidenced that this activity was not due to the original levels of carnosol, carnosic acid, and methyl carnosate (which only 47% remained after digestion) but due to their derivatives and digestion products.

Identification of the metabolites of ecabet bismuth in rat bile by liquid chromatography-electrospray ionization-tandem mass spectrometry

In the present study, a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI- MS/MS) method was developed for the screening and the structural elucidation of the metabolites of ecabet bismuth in rat bile. Solid-phase extraction cartridges were used for sample pre-treatment and a gradient liquid chromatographic system composed of 10 mM ammonium acetate buffer and methanol was used for chromatographic separation on a Phenomenex Kromasil C(18) column. The triple quadrupole mass spectrometer was employed to thoroughly detect and acquire the detailed MS/MS spectra of ecabet and its metabolites. By comparing the chromatographic retention behaviors, as well as the changes in molecular weight and full-scan MS/MS spectra of the potential metabolites with those of the parent compound, two main metabolites were identified as glucuronide conjugate of carbonylated ecabet (7-oxo-ecabet) and glucuronide conjugate of ecabet. Both two metabolites have not been reported in the literatures. The metabolic pathways of ecabet in rat were also proposed in this paper.

Biotransformation of two ent-Pimara-9(11),15-diene derivatives by Gibberella fujikuroi

The incubation of 19-hydroxy-13-epi-ent-pimara-9(11),15-diene (4) with Gibberella fujikuroi gave 8 alpha,19-dihydroxy-9 alpha,11alpha-epoxy-13-epi-ent-pimara-15-ene (6), 7-oxo-11 alpha,19-dihydroxy-13-epi-ent-pimara-8(9),15-diene (7), 7-oxo-11beta,19-dihydroxy-13-epi-ent-pimara-8(9),15-diene (9), and 8 alpha,19-dihydroxy-9 alpha,11 alpha:15,16-diepoxy-13-epi-ent-pimarane (11), while the feeding of 13-epi-ent-pimara-9(11),15-diene-19-oic acid (5) with this fungus afforded 1-oxo-2 alpha,9 alpha-dihydroxy-13-epi-ent-pimara-11,15-dien-19-oic acid (13), 1-oxo-2 beta,9 alpha-dihydroxy-13-epi-ent-pimara-11,15-dien-19-oic acid (14), 13-epi-ent-pimara-9(11),15-dien-1,19-dioic acid 1,2-lactone (15), and 1-oxo-12 beta-hydroxy-13-epi-ent-pimara-9(11),15-dien-19-oic acid (16). In both biotransformations, the main reaction was the epoxidation of the 9(11)-double bond, followed by rearrangement to afford allylic alcohols. The formation of lactone 15 represents the first time that a Baeyer-Villiger oxidation has been observed in a microbiological transformation with this fungus.

Augmentation by carnosic acid of apoptosis in human leukaemia cells induced by arsenic trioxide via upregulation of the tumour suppressor PTEN

Carnosic acid is a strong dietary antioxidant derived from rosemary. Here, we have demonstrated that carnosic acid decreased viability of the human promyelocytic leukaemia cell line, HL-60, in dose- and time-dependent manners, and induced G(1) arrest and apoptosis. Carnosic acid also augmented these effects when induced by a low (physiological) concentration of arsenic trioxide, which was associated with upregulation of p27 and activation of caspase-9. These effects appeared to be mediated by the induction of phosphatase and tensin homologue (PTEN) expression. These findings indicate that PTEN plays an important role in the coordinated induction of apoptosis and G(1) arrest by carnosic acid and arsenic trioxide. Carnosic acid may have potential as an adjuvant in arsenic trioxide-induced apoptosis therapy due to its anticipated safety and great potency in enhancing the apoptosis-inducing action of a low concentration of arsenic trioxide.

A large gene cluster in Burkholderia xenovorans encoding abietane diterpenoid catabolism

Abietane diterpenoids are defense compounds synthesized by trees that are abundant in natural environments and occur as significant pollutants from pulp and paper production. Burkholderia xenovorans LB400 has diverse catabolic capabilities and represents an important group of heterotrophic bacteria in soil environments. The genome sequence of LB400 revealed homologs of the dit genes of Pseudomonas abietaniphila BKME-9, which encode abietane diterpenoid degradation. LB400 grew on abietic acid (AbA), dehydroabietic acid (DhA), palustric acid (PaA), and 7-oxo-DhA. A Xeotron microarray set, with probes for 8450 of the estimated 9000 LB400 genes, was used to compare the transcriptomes of LB400 growing on DhA versus on succinate. On DhA, 97 genes were upregulated, 43 of which were within an 80-kb cluster located on the 1.47-Mbp megaplasmid of LB400. Upregulated genes in this cluster encode a permease, a ring-hydroxylating dioxygenase system (DitA), a ring-cleavage dioxygenase (DitC), a P450 monooxygenase (DitQ), and enzymes catalyzing beta-oxidation-type reactions. Disruption of the ditA1 gene, encoding the alpha-subunit of DitA, abolished growth on these abietanes. Analyses of the metabolism of abietanes by cell suspensions of wild-type LB400 and the ditA1 mutant indicate a convergent pathway, with 7-oxo-DhA as a common intermediate for ring hydroxylation by DitA. Also, 7-oxo-PaA was identified as a metabolite of both AbA and PaA. Sequence analysis indicates that genes encoding this pathway have been horizontally transferred among Betaproteobacteria and Gammaproteobacteria.

Molecular detection and diversity of novel diterpenoid dioxygenase DitA1 genes from proteobacterial strains and soil samples

Resin acids are tricyclic diterpenoids naturally synthesized by trees that are released from wood during pulping processes. Using a newly designed primer set, genes similar to that encoding the DitA1 catalytic alpha-subunit of the diterpenoid dioxygenase, a key enzyme in abietane resin acid degradation by Pseudomonas abietaniphila BKME-9, could be amplified from different Pseudomonas strains, whereas ditA1 gene sequence types representing distinct branches in the evolutionary tree were amplified from Burkholderia and Cupriavidus isolates. All isolates harbouring a ditA1-homologue were capable of growth on dehydroabietic acid as the sole source of carbon and energy and reverse transcription polymerase chain reaction analysis in three strains confirmed that ditA1 was expressed constitutively or in response to DhA, demonstrating its involvement in DhA-degradation. Evolutionary analyses indicate that gyrB (as a phylogenetic marker) and ditA1 genes have coevolved under purifying selection from their ancestral variants present in the most recent common ancestor of the genera Pseudomonas, Cupriavidus and Burkholderia. A polymerase chain reaction-single-strand conformation poylmorphism fingerprinting method was established to monitor the diversity of ditA1 genes in environmental samples. The molecular fingerprints indicated the presence ofa broad, previously unrecognized diversity of diterpenoid dioxygenase genes in soils, and suggest that other bacterial phyla may also harbour the genetic potential for DhA-degradation.

Fungal biotransformation products of dehydroabietic acid

Dehydroabietic acid (DHA) (1) is one of the main compounds in Scots pine wood responsible for aquatic and microbial toxicity. The degradation of 1 by Trametes versicolor and Phlebiopsis gigantea in liquid stationary cultures was followed by HPLC-DAD-ELSD. Both fungi rapidly degraded DHA relative to a control. More breakdown products were observed for T. versicolor than for P. gigantea. After 13 days, four compounds were identified by means of spectroscopic methods in P. gigantea cultures: 1beta-hydroxy-DHA (2), 1beta,7alpha-dihydroxy-DHA (3), 1beta,16-dihydroxy-DHA (5), and tentatively 1beta-hydroxy-7-oxo-DHA (4). In T. versicolor cultures, 1beta,16-dihydroxy-DHA (5), 7beta,16-dihydroxy-DHA (6), 1beta,7beta,16-trihydroxy-DHA (7), 1beta,16-dihydroxy-7-oxo-DHA (8), 1beta,15-dihydroxy-DHA (9), and 1beta,7alpha,16-trihydroxy-DHA (10) were identified after 9 days of incubation. Thus the biotransformation of 1 by the two fungi was different, with only 5 being produced by both strains. Compounds 3, 7, 8, and 10 are reported for the first time as natural products.

Improved aerobic biodegradation of abietic acid in ECF bleached kraft mill effluent due to biomass adaptation

Kraft pulp mill effluents contain elevated concentrations of resin acids, chiefly abietic and dehydroabietic acid, and other lipophilic wood constituents. Resin acids, if not efficiently removed during wastewater treatment, can be responsible for chronic toxicity in aquatic systems. The objective of this study was to investigate the biological removal of abietic acid (AbA) during the treatment of elemental chlorine free (ECF) kraft mill effluents in aerobic lagoons and to assess its improvement with time as a result of biomass adaptation. Under these conditions, the average removal efficiencies of AbA and BOD(5) attained in the aerobic lagoon were high and exceeded 80% and 95%, respectively. Microbial inhibition of non-acclimated and acclimated biomass by AbA was not detected in batch bioassays. Kinetic studies showed that the K(s) and V(m) values equalled 76.7 mg AbA/l and 0.011 l/h, respectively, for the non-acclimated biomass, and 1678 mg AbA/l and 0.13 l/h, respectively, for the acclimated biomass.

Theoretical Study of the Complexes of Horminone with Mg2+and Ca2+Ions and Their Relation with the Bacteriostatic Activity

The coordination of the horminone molecule with hydrated magnesium and calcium divalent ions was studied by means of the density functional theory. All-electron calculations were performed with the B3LYP/6-31G method. The first layer of the water molecules surrounding the metallic cations was included. It was found that the octahedral [horminone(O(a)-O(d))-Mg-(H(2)O)(4)](2+) complex is more stable than [Mg(H(2)O)(6)](2+). That is, horminone is able to displace two water units from the hexahydrated complex. This behavior does not occur for Ca(2+). Consistently, [horminone(O(a)-O(d))-Mg-(H(2)O)(4)](2+) has a greater metal-ligand binding energy than [horminone(O(a)-O(d))-Ca-(H(2)O)(4)](2+). The preference of horminone by Mg(2+) is enlightened by these results. Moreover, its electronic structure, as shown by huge changes in the atomic populations, is strongly perturbed by Mg(2+). Indeed, horminone, bonded to [Mg(H(2)O)(4)](2+), is able to cross the bacterial membrane cell. Once inside, [horminone(O(a)-O(d))-Mg-(H(2)O)(4)](2+) binds to rRNA phosphate groups yielding [horminone(O(a)-O(d))-Mg-(H(2)O)(PO(4)H(2))(PO(4)H(3))(2)](+). These results give insights into how horminone may inhibit the initial steps of protein synthesis. The stability of the studied systems is accounted for in terms of the calculated structural and electronic properties: Mg-O and Ca-O bond lengths, charge transfers, and binding energies.

Regio- and Stereo-selective Hydroxylation of Abietic Acid Derivatives by Mucor circinelloides and Mortierella isabellina

Mucor circinelloides and Mortierella isabellina hydroxylated dehydroabietic acid (DehA). DehA was converted regio- and stereo-selectively by whole cells of Mr. circinelloides to give 2alpha-hydroxydehydroabietic acid in a 75% molar conversion yield (11 mM from 14.7 mM DehA) after 72 h in the cultivation medium containing 3% (v/v) Tween 80. With cells of Ma. isabellina, under the same conditions, 20.5 mM (6.5 g l(-1)) 2-hydroxydehydroabietic acid (alpha/beta=81/19) was formed from 26.4 mM DehA.

Loblolly pine abietadienol/abietadienal oxidase PtAO (CYP720B1) is a multifunctional, multisubstrate cytochrome P450 monooxygenase

Cytochrome P450 monooxygenases (P450s) are important enzymes for generating some of the enormous structural diversity of plant terpenoid secondary metabolites. In conifers, P450s are involved in the formation of a suite of diterpene resin acids (DRAs). Despite their important role in constitutive and induced oleoresin defense, a P450 gene of DRA formation has not yet been identified. By using phylogenetic cluster analysis of P450-like ESTs from loblolly pine (Pinus taeda), functional cDNA screening in yeast (Saccharomyces cerevisiae), and in vitro enzyme characterization, we cloned and identified a multifunctional and multisubstrate cytochrome P450 enzyme, CYP720B1 [abietadienol/abietadienal oxidase (PtAO)]. PtAO catalyzes an array of consecutive oxidation steps with several different diterpenol and diterpenal intermediates in loblolly pine DRA biosynthesis. Recombinant PtAO oxidized the respective carbon 18 of abietadienol, abietadienal, levopimaradienol, isopimara-7,15-dienol, isopimara-7,15-dienal, dehydroabietadienol, and dehydroabietadienal with apparent Michaelis-Menten (K(m)) values of 0.5-5.3 muM. PtAO expressed in yeast also catalyzed in vivo oxidation of abietadiene to abietic acid, but with activity much lower than with abietadienol or abietadienal. Consistent with a role of DRAs in conifer defense, PtAO transcript levels increased upon simulated insect attack using methyl jasmonate treatment of loblolly pine. The multisubstrate, multifunctional P450 diterpene oxidase PtAO, in concert with expression of a family of single-product and multiproduct diterpene synthases, allows for formation of a diverse suite of DRA defense metabolites in long-lived conifers.

A cytochrome P450 involved in the metabolism of abietane diterpenoids by Pseudomonas abietaniphila BKME-9

Diterpenoids are naturally occurring plant compounds which have pharmaceutical properties. We have sequenced a 10.4-kbp extension of the dit cluster in Pseudomonas abietaniphila BKME-9, containing genes involved in abietane diterpenoid biodegradation. The ditQ gene was found to encode a cytochrome P450 monooxygenase, P450dit, and to be homologous to the tdtD gene of Pseudomonas diterpeniphila A19-6a. Knocking out ditQ had little effect on growth of BKME-9 on abietic acid but severely impaired growth on dehydroabietic acid (DhA) and palustric acid (PaA), increasing doubling times from 3.8 to 15 h on DhA and from 5.6 to 18.5 h on PaA. A xylE transcriptional fusion showed that transcription of ditQ was induced by a range of diterpenoids. Substrate binding assays of P450dit expressed in Escherichia coli revealed that DhA binds to the enzyme and yields a type I binding spectrum with a Kd of 0.4 microM. These results indicate that P450dit is involved in the metabolism of DhA and PaA and are consistent with its putative role in converting DhA to 7-hydroxy-DhA. Finally, an amino acid sequence identity of greater than 72% and conserved gene arrangement support the hypothesis that the dit gene cluster of P. abietaniphila BKME-9 and the tdt cluster of P. diterpeniphila A19-6a contain functional homologues.