Juraithip Wungsintaweekul

Effect of PEG molecular weight and linking chemistry on the biological activity and thermal stability of PEGylated trypsin.

PEGylated proteins are routinely used as therapeutics, but systematic studies of the effect of PEG molecular weight and linking chemistry on the biological activity and particularly the thermal stability of the conjugated protein are rarely made. Here, activated monomethoxypolyethylene glycol (mPEG)s (Mw 1100, 2000 and 5000 g/mol) were prepared using succinic anhydride (SA), cyanuric chloride (CC) or tosyl chloride (TC) and used to synthesise a library of trypsin conjugates. The enzyme activity (KM, Vmax and Kcat) of native trypsin and the mPEG-modified trypsin conjugates was compared using N-benzoyl-l-arginine p-nitroanilide (BAPNA) as a substrate, and their thermal stability determined using both BAPNA and N-alpha-benzoyl-l-arginine ethyl ester hydrochloride (BAEE) as substrates to measure amidase and esterase activity respectively. The effect of conjugate chemistry on trypsin autolysis was also examined at 40 degrees C. PEG-trypsin conjugates containing the higher molecular weight of mPEG (5000 g/mol) were more stable than free trypsin, and the conjugate containing CC-mPEG 5000 g/mol had the best thermal stability.

Biosynthesis of terpenoids: 1-deoxy-D-xylulose-5-phosphate reductoisomerase from Escherichia coli is a class B dehydrogenase.

1‐Deoxy‐D‐xylulose‐5‐phosphate is converted into 2‐C‐methyl‐D‐erythritol‐4‐phosphate by the catalytic action of 1‐deoxy‐D‐xylulose‐5‐phosphate reductoisomerase (Dxr protein) using NADPH as cofactor. The stereochemical features of this reaction were investigated in in vitro experiments with the recombinant Dxr protein of Escherichia coli using (4R)‐ or (4S)‐[4‐2H1]NADPH as coenzyme. The enzymatically formed 2‐C‐methyl‐D‐erythritol‐4‐phosphate was isolated and converted into 1,2:3,4‐di‐O‐isopropylidene‐2‐C‐methyl‐D‐erythritol; NMR spectroscopic investigation of this derivative indicated that only (4S)‐[4‐2H1]NADPH affords 2‐C‐methyl‐D‐erythritol‐4‐phosphate labelled exclusively in the HRe position of C‐1. Stereospecific transfer of HSi from C‐4 of the cofactor identifies the Dxr protein of E. coli as a class B dehydrogenase.

Mitragyna speciosa: Hairy Root Culture for Triterpenoid Production and High Yield of Mitragynine by Regenerated Plants

Hairy root cultures of Mitragyna speciosa were established by infection of Agrobacterium rhizogenes ATCC 15834 and maintained in McCown woody plant medium (WPM) supplemented with 0.5 mg/l naphthaleneacetic acid. The hairy roots were identified for the rooting genes loci of rolA and rolB by polymerase chain reaction. For studying the secondary metabolite production, the n-hexane extract of the hairy roots was prepared and the compounds were isolated by silica gel column chromatography, affording triterpenoids (ursolic acid and oleanolic acid) and phytosterols (β-sitosterol and stigmasterol). The shoots from the hairy root cultures were regenerated and differentiated to the plantlets. For micropropagation, shoot multiplication was successfully induced from the axillary buds of the regenerated plantlets in WPM supplemented with 0.1 mg/l thidiazuron. The mitragynine contents of 5-monthold regenerated plants and in vitro plantlets (germinated from seeds) were determined using the TLC-densitometric method. The regenerated plants contained (14.25 ± 0.25) mg/g dry wt mitragynine, whereas the in vitro plantlets contained (4.45 ± 0.09) mg/g dry wt.

Development of indirect competitive ELISA for quantification of mitragynine in Kratom (Mitragyna speciosa (Roxb.) Korth.)

Monoclonal antibody (MAb) against mitragynine (MG), an analgesic alkaloid from Kratom leaves (Mitragyna speciosa), was produced. MG was coupled to carrier proteins employing either 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS), a zero-length cross linker or a 5-carbon length glutaraldehyde cross linker. To confirm the immunogenicity, the hapten numbers were determined using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Preparation of the MAb was accomplished by the electrofusion method. Hybridoma 1A6 that was constructed from the fusion between splenocytes of EDC/NHS conjugate immunized mice and SP2/0-Ag14 myeloma cells was selected, cloned twice and expanded. The cross-reactivities (CRs) of this MAb 1A6 with a series of indole alkaloids were 30.54%, 24.83% and 8.63% for speciogynine, paynantheine and mitraciliatine, respectively. Using this MAb, an indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed with a measurement range of 32.92-250 μg/mL. Quantitative analysis of the MG contents in plant samples by icELISA correlated well with the standard high performance liquid chromatography method (R(2)=0.994). The MAb against mitragynine provided a tool for detection of MG in Kratom preparations.

Cloning and expression of 1-deoxy-d-xylulose 5-phosphate synthase cDNA from Croton stellatopilosus and expression of 2C-methyl-d-erythritol 4-phosphate synthase and geranylgeranyl diphosphate synthase, key enzymes of plaunotol biosynthesis

1-Deoxy-d-xylulose 5-phosphate synthase (DXS, EC: 4.1.3.37), the first enzyme in the 2C-methyl-d-erythritol 4-phosphate (MEP) pathway, is known to be responsible for the rate-limiting step of isoprenoid biosynthesis in Escherichia coli and Arabidopsis thaliana. In this study, the dxs gene from Croton stellatopilosus, designated csdxs, was cloned from leaf tissue using the rapid amplification of cDNA ends (RACE) technique. Leaves of C. stellatopilosus contain plaunotol, an acyclic diterpene alcohol. The csdxs cDNA containing the open reading frame of 2163 base pairs appeared to encode a polypeptide of 720 amino acids. Analysis of the deduced amino acid sequence revealed that the NH(2)-terminus of CSDXS carried a chloroplast transit peptide, a thiamine diphosphate binding site, and a transketolase motif, which are the important characteristics of DXS enzymes in higher plants. Multiple alignments of CSDXS with other plant DXSs have indicated that CSDXS has identity ranging between 68% and 89%. Expression levels of csdxs and genes encoding key enzymes in the plaunotol biosynthetic pathway, namely 2C-methyl-d-erythritol 4-phosphate synthase (meps) and geranylgeranyl diphosphate synthase (ggpps), were analysed by measuring transcript levels in leaves of different developmental stages. The results showed that dxs, meps, and ggpps are all active in young leaves prior to full expansion when plaunotol is synthesised from the DXP precursor in chloroplasts. The dense presence of chloroplasts and oil globules in the palisade cells of these leaves support the view that these genes are involved in plaunotol biosynthesis in chloroplast-containing tissues.

Stereochemical course of the reduction step in the formation of 2-C-methylerythritol from the terpene precursor 1-deoxyxylulose in higher plants

Feeding of 1-deoxy-D-[3-2H]xylulose to leaves of the tree Liriodendron tulipifera affords 2-C-methyl-D-erythritollabelled specifically in the HSi position of C-1.

Establishment of Croton stellatopilosus Suspension Culture for Geranylgeraniol Production and Diterpenoid Biosynthesis

Diterpenoids in higher plants are biosynthesized from isoprene units obtained from two distinct pathways: the mevalonate pathway and the deoxyxylulose phosphate pathway. The metabolic partitioning of both pathways in plant species is dependent upon the type of culture. In order to study the diterpenoid biosynthesis in Croton stellatopilosus cell culture, callus culture was firstly induced from C. stellatopilosus young leaves in Murashige and Skoog (MS) medium in the presence of 1.0 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D), 1.0 mg/l benzyladenine (BA), 3% (w/v) sucrose and 0.8% (w/v) agar. The suspension culture was further induced from its callus in the same medium without gelling agent. Detection of diterpenoid accumulation by gas chromatography-mass spectrometry revealed that a cell culture could accumulate a low amount of geranylgeraniol (GGOH) and a high content of fatty acids and phytosterols. To improve the GGOH production, the culture conditions were optimized by medium manipulation in terms of hormonal factors. The growth rates of cell cultures were similar in all kinds of media. The GGOH production curve indicated that GGOH plays an important role as a primary metabolite in the cell culture. The optimum medium for GGOH production was MS medium supplemented with 2.0 mg/l 2,4-D and 2 mg/l BA that could produce GGOH with a yield of 1.14 mg/g FW.

Preparation of a monoclonal antibody against notoginsenoside R1, a distinctive saponin from panax notoginseng, and its application to indirect competitive elisa

We have prepared a monoclonal antibody against notoginsenoside R1, a primary active constituent of Sanqi ginseng (roots of Panax notoginseng). The monoclonal antibody was raised by immunizing BALB/c male mice with notoginsenoside R1-bovine albumin conjugates following cell fusion via electroporation. This method has been shown to be very effective for producing hybridomas with excellent antibody prevalence following cell fusion of their splenocytes with cells of the myeloma cell line SP2/0. Of all the hybridomas secreting a monoclonal antibody against notoginsenoside R1, only the 1A1P cell line produces a highly specific antibody to this compound. Surprisingly, the cross-reactivity of this monoclonal antibody for ginsenoside Rg1 and ginsenoside Re, derivatives of protopanaxatriol, was below 1.02% in a competitive immunoassay. Based on this characteristic of the monoclonal antibody, an indirect competitive ELISA (range of measurement 0.56-9 µg/mL) was established and applied as a quality control method. In conclusion, the developed immunoassay was easy to handle and reliable for the analysis of notoginsenoside R1 in Sanqi ginseng products without requiring a pretreatment.

Investigation of enhancing activity and skin irritation of Zingiber officinale, Zingiber cassumunar and Curcuma zedoaria

The penetration enhancing effect of essential oils extracted from rhizomes of Zingiber officinale, Zingiber cassumunar and Curcumar zedoaria on the skin permeation of diclofenac sodium was evaluated in vitro using modified Franz diffusion cell and Wistar rat skin. The essential oils were tested at 1, 3 and 5% (w/v) in the vehicle hydroalcoholic mixture (ethanol: water (1:1 v/v)). The skin permeation of diclofenac sodium was remarkably enhanced in the presence of these three essential oils. Overall, the rank order of the enhancing activities of these oils was Zingiber officinale > Zingiber cassumunar > Curcuma zedoaria. Furthermore, the essential oil at 5% appeared to give the greatest enhancement. For the in vivo skin irritation study, these oils were tested at 1 and 5% in the vehicle and at 100%. These test solutions including the vehicle were applied to the abdominal surfaces of the Wistar rats and kept in contact with these areas for 24 h. After a biopsy technique, the skin irritation was evaluated under microscopic observation and histological scores were used as an index of skin damage caused by the test compounds. The skin irritation study revealed that the vehicle had no discernible effects in histological appearance in rat skin. The essential oils at concentrations of 1 and 5% in hydroalcoholic mixture and at 100% were found to cause skin irritation in different degrees. The most severe skin damage was observed with the 1% of these oils whereas the 5% of these oils were classified as mild irritants.

Molecular cloning and functional characterization of three terpene synthases from unripe fruit of black pepper (Piper nigrum)

To identify terpene synthases (TPS) responsible for the biosynthesis of the sesquiterpenes that contribute to the characteristic flavors of black pepper (Piper nigrum), unripe peppercorn was subjected to the Illumina transcriptome sequencing. The BLAST analysis using amorpha-4,11-diene synthase as a query identified 19 sesquiterpene synthases (sesqui-TPSs), of which three full-length cDNAs (PnTPS1 through 3) were cloned. These sesqui-TPS cDNAs were expressed in E. coli to produce recombinant enzymes for in vitro assays, and also expressed in the engineered yeast strain to assess their catalytic activities in vivo. PnTPS1 produced β-caryophyllene as a main product and humulene as a minor compound, and thus was named caryophyllene synthase (PnCPS). Likewise, PnTPS2 and PnTPS3 were, respectively, named cadinol/cadinene synthase (PnCO/CDS) and germacrene D synthase (PnGDS). PnGDS expression in yeast yielded β-cadinene and α-copaene, the rearrangement products of germacrene D. Their kcat/Km values (20-37.7 s-1 mM-1) were comparable to those of other sesqui-TPSs. Among three PnTPSs, the transcript level of PnCPS was the highest, correlating with the predominant β-caryophyllene biosynthesis in the peppercorn. The products and rearranged products of three PnTPSs could account for about a half of the sesquiterpenes in number found in unripe peppercorn.