Biomedical subjects

Guo-Qiang Chen

Publications and source records attributed to Guo-Qiang Chen.

At least 55 records · Page 3Linked to original sources

PubMed2005

Effects of crystallization of polyhydroxyalkanoate blend on surface physicochemical properties and interactions with rabbit articular cartilage chondrocytes.

As a new member of polyhydroxyalkanoate (PHA) family, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) has better mechanical properties compared with poly(3-hydroxybutyrate) (PHB). Still, many properties of PHBHHx and its blend with PHB may be exploited for a wide range of applications, such as tissue engineering and drug delivery. In this study, PHBHHx was found to be completely miscible with PHB in their blends. Crystallization behavior of these polyester blends played an important role in determination of the surface physicochemical properties including surface free energy, chemical states and polarity, and could subsequently govern the cellular responses. Interaction between PHB and PHBHHx influenced the non-dispersion surface free energy component, which governed the total surface free energy. It was shown that the blend with a 1:1 ratio of PHB/PHBHHx possessed the highest surface free energy, which was the most optimal material for chondrocytes adhesion. After 24 h, the amount of chondrocytes adhered on films of PHB/PHBHHx (1:1) was 2.1 x 10(4)cells/cm(2), 5-times more compared with that on the PHB films (0.4 x 10(4)cells/cm(2)). The polarity of the blends increased with decreasing crystallinity. After 8 days of cultivation, the chondrocytes attached on PHB films were surrounded by both collagen II and collagen X, the amount of extracellular collagen X decreased with increasing polarity contributed by increasing PHBHHx content in the blend, while chondrocytes changed shapes from spherical to flat with increasing polarity. It indicated that endochondral ossification of chondrocytes was remarkably influenced by the crystallinity of the polyesters.

3-Hydroxybutyric Acid↗

PubMed2005

The application of polyhydroxyalkanoates as tissue engineering materials.

Polyhydoxyalkanoates (PHA) are polyesters produced by microorganisms under unbalanced growth conditions. They are generally biodegradable and thermoprocessable, making them attractive as biomaterials for applications in both conventional medical devices and tissue engineering. Over the past years, PHA, particularly poly 3-hydroxybutyrate (PHB), copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate (PHBV), poly 4-hydroxybutyrate (P4HB), copolymers of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx) and poly 3-hydroxyoctanoate (PHO) and its composites have been used to develop devices including sutures, repair devices, repair patches, slings, cardiovascular patches, orthopedic pins, adhesion barriers, stents, guided tissue repair/regeneration devices, articular cartilage repair devices, nerve guides, tendon repair devices, bone marrow scaffolds, and wound dressings. The changing PHA compositions also allow favorable mechanical properties, biocompatibility, and degradation times within desirable time frames under specific physiological conditions. This paper reviews what have been achieved in the PHA tissue engineering area and concluded that the PHA prospective will look very bright in the near future.

3-Hydroxybutyric Acid↗

PubMed2005

Enhanced vascular-related cellular affinity on surface modified copolyesters of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx).

Random copolyester of 3-hydroxybutyrate and 3-hydroxyhexanoate, short as PHBHHx, was surface modified by ammonia plasma treatment and/or fibronectin coating, respectively. The improved results were demonstrated by better growth of human umbilical vein endothelial cells (HUVECs) and rabbit aorta smooth muscle cells (SMCs) on the surface of ammonia plasma-treated PHBHHx coated with fibronectin (PFn-PHBHHx), compared with the fibronectin-coated (Fn-PHBHHx) or uncoated PHBHHx, respectively, although XPS analysis and ELISA demonstrated higher fibronectin adsorption on Fn-PHBHHx than on PFn-PHBHHx. Confocal microscopy observation showed that the specific co-localization of fibronectin with F-actin was impaired on PFn-PHBHHx, while it was almost lost on Fn-PHBHHx compared with pristine PHBHHx or plasma-treated PHBHHx (P-PHBHHx). These were attributed to the generation of new nitrogen- and oxygen-containing groups on the PHBHHx surface by the ammonia plasma treatment, which led to increased polar components that enhanced polymer surface energy and hydrophilic properties on P-PHBHHx. The most prominent effect of PFn-PHBHHx was its stimulation of HUVECs proliferation. HUVECs on PFn-PHBHHx formed a confluent monolayer after 3 days of incubation, while SMCs were unable to form a sub-confluent layer. The above evidences revealed that PFn-PHBHHx would benefit endotheliazation rather than SMCs proliferation. We therefore believed that PFn-PHBHHx would be a promising material as a luminal surface of vascular grafts.

3-Hydroxybutyric Acid↗

PubMed2005

As2O3 enhances the anion transport activity of band 3 and the action is related with the C-terminal 16 residues of the protein.

Successful application of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia (APL) has been attracting worldwide interest, but the exact mechanism for the action of As2O3 remains somewhat obscure. In the present work, we show for the first time that As2O3 facilitates the DIDS-sensitive anion transport activity of band 3 protein in red blood cells (RBCs) isolated from normal adults and APL patients. To elucidate the effect of As2O3 on band 3 protein, constructs encoding the full length of the band 3 transmembrane domain (mdb3) and its C-terminal deletion forms were transfected into yeast cells by a yeast display system. The results demonstrate that deletion of the C-terminal 16 residues of mdb3 (mdb3-d16) does not affect anion transport activity of mdb3 or its sensitivity to DIDS, but decreases its sensitivity to As2O3 in the yeast cell. More intriguingly, the forced expression of intact mdb3 by transfection significantly induces cell apoptosis in HeLa cells, to a higher degree than in cells transfected with mdb3-d16 or empty vector. Expression of activated caspase 3 in HeLa cells also indicates that the C-terminal 16 residues are important for mdb3-mediated apoptosis in cells treated with As2O3. Our results provide the first evidence that As2O3 enhances the anion transport activity of band 3 and the action is related with the C-terminal 16 residues of the protein.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed2005

Specific identification of (R)-3-hydroxyacyl-ACP: CoA transacylase gene from Pseudomonas and Burkholderia strains by polymerase chain reaction.

Polyhydroxyalkanoates (PHA) were biodegradable thermoplastics. Due to their broad applications, direct biosynthesis of PHA from inexpensive substrates, such as carbohydrates, is actively pursued. It has been recently revealed that (R)-3-hydroxyacyl-ACP: CoA transacylase (PhaG) played an important role in this pathway. In this study, a polymerase chain reaction (PCR) protocol was developed for the rapid and specific identification of phaG gene from various bacteria. Using the PCR strategy, the complete open reading frames of two phaG genes from Pseudomonas stutzeri 1317 and Pseudomonas nitroreducens 0802 were cloned from the genomic DNA and functionally expressed in Pseudomonas putida PHAGN-21. Furthermore, this strategy was successful applied in non-Pseudomonas strains, such as Burkholderia. These results suggest that PhaG-mediated pathway of medium-chain-length polyhydroxyalkanoates was widespread among bacteria.

Acyltransferases↗

PubMed2005

[Construction of an antisense RNA recombinant adenovirus vector of the human PDE5A1 gene promoter].

OBJECTIVE: To construct an antisense RNA recombinant adenovirus vector of the human PDE5A1 promoter gene. METHODS: A cDNA fragment containing the human PDE5A1 promoter and the human PDE5A1-specific exon was determined according to the gene bank. The antisense RNA fragment was synthesized artificially and subcloned into the pENTR. Then, the sequence of pENTR fragment was detected, and the recombinant adenovirus vector pAd/CMV/V5/antisense-PDE5A1 was constructed by LR reaction with the Gateway expression system. The identified recombinant adenovirus plasmid was digested with Pac I and transformed into 293A cells to package recombinant adenovirus particles. The recombinant adenovirus particles were tested with PCR technique and purified after acquisition by CsCl density gradient ultracentrifugation. RESULTS: The sequencing result showed a 145 bp fragment in pENTR, which was proved to be the domain of the antisense RNA fragment. PCR confirmed that the antisense RNA fragment was cloned into the recombinant adenovirus vector pAd/CMV/V5/antisense-PDE5A1 successfully and could infect 293A cells. The titer of virus stocks was up to 10(8) - 10(10)/microl after purification. CONCLUSION: With the Gateway expression system, the culturing and reproduction of 293A cells can reproduce recombinant adenovirus pAd/CMV/V5-DEST successfully, and the recombinant adenovirus vector can meet the need of in vivo gene transfection in laboratory studies.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed2005

[Synthesis of medium-chain-length polyhydroxyalkanoate (mcl PHA) in type I PHA synthase negative mutant of Aeromonas hydrophila].

Aeromonas hydrophila CGMCC 0911 possessing type I polyhydroxyalkanoate (PHA) synthase gene (phaC) only accumulate copolyesters consisting of 3-hydroxybutyrate (3HB) and 3-hydroxyhexanoate (3HHx), abbreviated as PHBHHx, from lauric acid as sole carbon source but not from glucose. The gene encoding type I PHA synthase was interrupted by insertion of a chloramphenicol resistance gene (Cm). Conjugation of suicide plasmid pFH10 transformed A. hydrophila CGMCC 0911 into a recombinant organism with the disrupted type I PHA synthase gene (phaC:: Cm) , through an in vivo homologous recombination process, type I phaC of A. hydrophila genome was replaced by the disrupted phaC, and Cm gene was integrated into the genome of A. hydrophila, resulting in type I phaC-negative mutant, which was proved by DNA sequencing. Results of GC analysis showed that this mutant could not accumulate PHBHHx again but accumulate medium-chain-length (mcl) PHA from lauric acid or glucose as carbon source, clearly indicating the existence of another type I PHA synthase in the wild type A. hydrophila. It will play its function and accumulate mcl PHA only when type I PHA synthase was inactivated. into the genome of A. hydrophila, resulting in type I phaC-negative mutant, which was proved by DNA sequencing. Results of GC analysis showed that this mutant could not accumulate PHBHHx again but accumulate medium-chain-length (mcl) PHA from lauric acid or glucose as carbon source, clearly indicating the existence of another type II PHA synthase in the wild type A. hydrophila. It will play its function and accumulate mcl PHA only when type I PHA synthase was inactivated.

Acyltransferases↗

PubMed2005

Hypoxia-simulating agents and selective stimulation of arsenic trioxide-induced growth arrest and cell differentiation in acute promyelocytic leukemic cells.

BACKGROUND AND OBJECTIVES: We recently reported that hypoxia-mimetic agents cobalt chloride (CoCl2 CoCl2 ) and desferrioxamine (DFO) could induce differentiation of acute myeloid leukemic (AML) cells. Here, we investigate whether these two agents influence the in vitro differentiation-inducing effect of arsenic trioxide (As2O3) on AML cells, an effective drug for the treatment of acute promyelocytic leukemia (APL) that is a unique subtype of AML with a specific fusion protein, PML-RARalpha. DESIGN AND METHODS: The APL cell line NB4 and non-APL promonocytic leukemic cell line U937 were treated with As2O3 (0.5 microM) combined with CoCl2 (50 microM) or DFO (10 microM). The U937/PR9 subclone, whose expression of PML-RARalpha protein can be induced by Zn2+, was also investigated. Cellular differentiation was evaluated by morphological criteria and myeloid differentiation-related antigens and marker gene expression. The hypoxia-inducible factor-1alpha (HIF-1alpha) mRNA and protein were detected, respectively, by semi-quantitative/real-time quantitative reverse transcription polymerase chain reaction and immunoblots. PML-RARalpha protein was also analyzed. RESULTS: CoCl2 and DFO potentiated the growth-inhibiting and differentiation-inducing effects of low-dose As2O3, the latter enhancing CoCl2 and DFO-induced accumulation of HIF-1alpha protein in NB4 cells but not in U937 cells. These two hypoxia-mimetic agents also accelerated As2O3-induced modulation and degradation of PML-RARalpha protein in NB4 cells. Furthermore, inducible expression of the fusion gene restored the co-operative effects of As2O3 and CoCl2/DFO on U937/PR9 cells in terms of growth arrest, differentiation induction and HIF-1alpha protein accumulation. INTERPRETATION AND CONCLUSIONS: Mimicked hypoxia enhanced As2O3-induced differentiation, in which HIF-1alpha and PML/RARalpha proteins played an important role. These data provide new insights into the understanding of the mechanisms of the action of As2O3 in the treatment of patients with APL.

Antineoplastic Agents↗

PubMed2004

Engineered Aeromonas hydrophila for enhanced production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with alterable monomers composition.

Aeromonas hydrophila 4AK4 produces poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) containing 3-hydroxybutyrate (3HB) and about 15 mol% 3-hydroxyhexanoate (3HHx) from dodecanoate. To study the factors affecting the monomer composition and PHBHHx content, genes encoding phasin (phaP), PHA synthase (phaC) and (R)-specific enoyl-CoA hydratase (phaJ) from Aeromonas punctata (formerly named Aeromonas caviae) were introduced individually or jointly into A. hydrophila 4AK4. The phaC gene increased 3HHx fraction more significantly than phaP, while phaJ had little effect. Expression of phaC alone increased the 3HHx fraction from 14 to 22 mol%. When phaC was co-expressed with phaP and phaJ, the 3HHx fraction increased from 14 to 34 mol%. Expression of phaP or phaC alone or with another gene enhanced PHBHHx content up to 64%, cell dry weight (CDW) as much as 4.4 gL(-1) and PHBHHx concentration to 2.7 gL(-1) after 48 h in shake flask culture. The results suggest that a higher PHA synthase activity could lead to a higher 3HHx fraction and PHBHHx content. Co-expression of phaJ with phaC or phaP would favor PHA accumulation, although over-expression of phaJ did not affect PHA synthesis much. In addition, inhibition of beta-oxidation by acrylate in A. hydrophila 4AK4 enhanced PHBHHx content. However, no monomers longer than 3HHx were detected. The results show that genetic modification of A. hydrophila 4AK4 enhanced PHBHHx production and altered monomer composition of the polymer.

3-Hydroxybutyric Acid↗

PubMed2004

Combined effects of As4S4 and imatinib on chronic myeloid leukemia cells and BCR-ABL oncoprotein.

Imatinib (STI571, Gleevec) is a tailored drug for chronic myelogenous leukemia (CML), whereas arsenic compounds were used as ancient remedies for CML with certain efficacy. The aim of this study was to investigate the potential benefit of combination therapy with imatinib and arsenic sulfide (As(4)S(4)). Analysis of cell proliferation and clonogenic ability showed that As(4)S(4) and imatinib exerted synergistic effects on both K562 cells and fresh CML cells. The effective concentrations on fresh CML cells were pharmacokinetically available in vivo but had much less inhibitory effect on CD34(+) cells from the nonleukemic donors. Examination of cell cycles showed that As(4)S(4) induced G(2)/M arrest whereas imatinib induced G(1) arrest. Using a number of parameters such as morphology, annexin V/propidium iodide (PI), mitochondrial transmembrane potential, caspase-3 activity, and Fas/Fas-L, the synergistic effects were revealed on induction of cell apoptosis, largely through the mitochondrial pathway. The 2 drugs also exhibited a synergistic effect in targeting BCR-ABL protein. While As(4)S(4) triggered its degradation and imatinib inhibited its tyrosine kinase activity, combined use of the 2 led to lower protein/enzymatic activity levels of BCR-ABL. Our in vitro data thus strongly suggest a potential clinical application of imatinib and As(4)S(4) combination on CML.

Antineoplastic Agents↗

PubMed2004

Protein kinase Cdelta mediates retinoic acid and phorbol myristate acetate-induced phospholipid scramblase 1 gene expression: its role in leukemic cell differentiation.

Although phospholipid scramblase 1 (PLSCR1) was originally identified based on its capacity to promote transbilayer movement of membrane phospholipids, subsequent studies also provided evidence for its role in cell proliferation, maturation, and apoptosis. In this report, we investigate the potential role of PLSCR1 in leukemic cell differentiation. We show that all-trans retinoic acid (ATRA), an effective differentiation-inducing agent of acute promyelocytic leukemic (APL) cells, can elevate PLSCR1 expression in ATRA-sensitive APL cells NB4 and HL60, but not in maturation-resistant NB4-LR1 cells. ATRA- and phorbol 12-myristate 13-acetate (PMA)-induced monocytic differentiation is accompanied by increased PLSCR1 expression, whereas only a slight or no elevation of PLSCR1 expression is observed in U937 cells differentiated with dimethyl sulfoxide (DMSO), sodium butyrate, or vitamin D3. Cell differentiation with ATRA and PMA, but not with vitamin D3 or DMSO, results in phosphorylation of protein kinase Cdelta (PKCdelta), and the PKCdelta-specific inhibitor rottlerin nearly eliminates the ATRA- and PMA-induced expression of PLSCR1, while ectopic expression of a constitutively active form of PKCdelta directly increases PLSCR1 expression. Finally, decreasing PLSCR1 expression with small interfering RNA inhibits ATRA/PMA-induced differentiation. Taken together, these results suggest that as a protein induced upon PKCdelta activation, PLSCR1 is required for ATRA- and PMA-triggered leukemic cell differentiation.

Cell Differentiation↗

PubMed2004

Polyhydroxyalkanoate synthases PhaC1 and PhaC2 from Pseudomonas stutzeri 1317 had different substrate specificities.

The whole polyhydroxyalkanoate (PHA) synthesis gene locus of Pseudomonas stutzeri strain 1317 containing PHA synthase genes phaC1Ps, phaC2Ps and PHA depolymerase gene phaZPs was cloned using a PCR cloning strategy. The sequence analysis results of the phaC1Ps, phaC2Ps and phaZPs showed high homology to the corresponding pha loci of the known Pseudomonas strains, respectively. PhaC1Ps and PhaC2Ps were functionally expressed in recombinant Escherichia coli strains and their substrate specificity was compared. The results demonstrated that PhaC1Ps and PhaC2Ps from P. stutzeri 1317 had different substrate specificities when expressed in E. coli. In details, PhaC2Ps could incorporate both short-chain-length 3-hydroxybutyrate and medium-chain-length 3-hydroxyalkanoates (mcl 3HA) into PHA, while PhaC1Ps only favored mcl 3HA for polymerization.

Acyltransferases↗

PubMed2004

Metabolic engineering for the production of copolyesters consisting of 3-hydroxybutyrate and 3-hydroxyhexanoate by Aeromonas hydrophila.

Aeromonas hydrophila 4AK4 was able to synthesize copolyesters consisting of 3-hydroxybutyrate (3HB) and about 15 mol-% 3-hydroxyhexanoate (3HHx) (PHBHHx) when grown in long chain fatty acids such as dodecanoate regardless of growth conditions. To regulate the unit fraction in PHBHHx, phbA and phbB genes encoding beta-ketothiolase and acetoacetyl-CoA reductase in Ralstonia eutropha, were introduced into A. hydrophila 4AK4. When gluconate was used as cosubstrate of dodecanoate, the recombinant produced PHBHHx containing 3-12 mol-% 3HHx, depending on the gluconate concentration in media. Vitreoscilla hemoglobin gene, vgb, was also introduced into the above recombinant, resulting in improved PHBHHx content from 38 to 48 wt.-% in shake flask study. Fermentor studies also showed that increased gluconate concentration in medium containing dodecanoate promoted the recombinant strain harboring phbA and phbB genes to incorporate more 3HB unit into PHBHHx, resulting in reduced 3HHx fraction. Recombinant A. hydrophila harboring phbA, phbB and vgb genes demonstrated better PHBHHx productivity and higher conversion efficiency from dodecanoate to PHBHHx than those of the recombinant without vgb in fermentation study. Combined with the robust growth property and simple growth requirement, A. hydrophila 4AK4 appeared to be a useful organism for metabolic engineering.

3-Hydroxybutyric Acid↗

PubMed2004

Chiral recognition of zinc(II) ion complexes composed of bicyclo[3.3.0] octane-2,6-diol and s-naproxen probed by collisional-induced dissociation.

Chiral recognition of racemic bicyclo[3.3.0] octane-2,6-diol(B) was achieved in the gas phase using s-Naproxen(A) as reference, using the kinetics of competitive unimolecule dissociation of tetrameric zinc(II)-bound complexes by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer(ESI-FTMS). As undergoing a mild competitive collision-induced dissociation(CID) experiment with a constant pressure argon gas introduced by leak valve, the tetrameric cluster ion [A(2)B(2)Z(n)(II)-H](+) forms only two trimeric ions and R(chiral) is subsequently obtained in the kinetic method. Further studies obtained the difference of Gibbs free energy of [ABZ(n)(II)-H](+)(Delta Delta G(ABZn(II)-H](+))) by dissociating [A(2)BZ(n)(II)-H](+), resulting two fragment ions [ABZ(n)(II)-H](+) and [A(2)Z(n)(II)-H](+), which can be established to a linear relationship between Delta Delta G([ABZn(II)-H](+)) and R(chiral)' basing on the kinetic method. The value of R(chiral)' suggested that Delta Delta G([ABZn(II)-H](+)) could be regarded as zero. Meanwhile, dissociation of [AB(2)Z(n)(II)-H](+) generated only one daughter ion [ABZ(n)(II)-H](+) in a stable pressure. Thus, a linear relationship was established between the difference of Gibbs free energy of [AB(2)Z(n)(II)-H](+)(Delta Delta G([AB(2)Zn(II)-H](+))) and R(chiral)" if the Delta Delta G([ABZn(II)-H](+)) can be negligible. Because there is also a linear relationship of R(chiral) in the tetrameric ion [A(2)B(2)Z(n)(II)-H](+) and the Gibbs energy difference of trimeric cluster ion [A(2)BZ(n)(+)(II)-H](Delta Delta G([A(2)BZn(II)-H](+))) plus that of [AB(2)Z(n)(II)-H](+), Delta Delta G([A(2)BZ(n)(II)-H]+]) is easy to be calculated in the dissociation process of tetrameric ion. Stable of R(chiral), R(chiral)' and R(chiral)" under different pressures show T(eff) does not affect the chiral recognition of cluster ions in the condition selected. If an only-one-daughter-ion fragment process of [A(2)BZ(n)(II)-H](+) was existed, R(chiral)''' relating to this dissociation would be calculated just like R(chiral)" of [AB(2)Z(n)(II)-H](+) does. Conclusion was obtained that [A(2)BZ(n)(II)-H](+) makes more contribution to chiral recognition of tetrameric ion measured by kinetic method than [AB(2)Z(n)(II)-H](+) does as R(chiral)''' and R(chiral)" were applied as index to evaluate the Gibbs free energy difference of these two trimeric cluster ions. Further discussion shows that steric interactions and pi-pi stacking interactions are the major factors responsible for the observed efficient chiral recognition in this system.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2004

Attachment, proliferation and differentiation of osteoblasts on random biopolyester poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) scaffolds.

Rabbit bone marrow cells were inoculated on 3D scaffolds of poly(lactic acid) (PLA), poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) to evaluate their in vitro biocompatibilities. It was found that PHBHHx had the best performance on attachment, proliferation of bone marrow cells. The cells on PHBHHx scaffolds presented typical osteoblast phenotypes: round cell shape, high alkaline phosphotase (ALP) activity, strong calcium deposition, and fibrillar collagen synthesis. After incubation for 10 days, cells grown on PHBHHx scaffolds were approximately 2x10(5)ml(-1), 40% more than that on PHB scaffolds and 60% more than that on PLA scaffolds. ALP activity of the cells grown on PHBHHx scaffolds was up to about 65U/g scaffolds, 50% higher than that of PHB and PLA, respectively. The scanning electronic microscopy (SEM) results showed that PHBHHx scaffolds had the appropriate roughness for osteoblast attachment and proliferation comparing with PHB and PLA. All these indicated that PHBHHx was a suitable biomaterial for osteoblast attachment, proliferation and differentiation from bone marrow cells.

3-Hydroxybutyric Acid↗

PubMed2004

Production of 3-hydroxydecanoic acid by recombinant Escherichia coli HB101 harboring phaG gene.

Heterogenous expression of (R)-3-hydroxydecanoyl-ACP:CoA transacylase gene (phaG) isolated from Pseudomonas putida in Escherichia coli HB101 led to the extracellular production of 3-hydroxydecanoic acid (3HD) in a growth medium consisting of carbon source non-related to 3HD structure, while no 3HD was detected in the growth media inoculated with wild type E. coli HB101 and recombinant E. coli HB101 harboring vector pBluescript SK- only. 3HD production by E. coli HB101 (pLZZGPp) harboring phaG from fructose was 587 mg/l, approximately three times that from cultivation in glucose under same culture conditions. 3HD production was affected by timing of fructose addition and fructose concentration in the culture. As an inhibitor of fatty acid de novo synthesis, the presence of triclosan in the culture could increase 3HD production by E. coli HB101 (pLZZGPp) by about 20-40%. The results further confirmed that (R)-3-hydroxydecanoyl-ACP:CoA transacylase (PhaG) provides 3HD precursors for medium-chain-length polyhydroxyalkanoate synthesis. At the same time, this phenomenon showed that recombinant organisms can be used for production of certain fine chemicals such as hydroxyalkanoic acids.

Acyltransferases↗

PubMed2004

Thioesterase II of Escherichia coli plays an important role in 3-hydroxydecanoic acid production.

3-Hydroxydecanoic acid (3HD) was produced in Escherichia coli by mobilizing (R)-3-hydroxydecanoyl-acyl carrier protein-coenzyme A transacylase (PhaG, encoded by the phaG gene). By employing an isogenic tesB (encoding thioesterase II)-negative knockout E. coli strain, CH01, it was found that the expressions of tesB and phaG can up-regulate each other. In addition, 3HD was synthesized from glucose or fructose by recombinant E. coli harboring phaG and tesB. This study supports the hypothesis that the physiological role of thioesterase II in E. coli is to prevent the abnormal accumulation of intracellular acyl-coenzyme A.

Decanoic Acids↗

PubMed2004

[Regulation of hypoxia-inducible factor-1alpha expression].

Hypoxia-inducible factor-1(HIF-1) is a major transcriptional regulator of O2 homeostasis, and plays a key role in physiology, and pathophysiology, and also in tumor pathogenesis. HIF-1 is a heterodimer consisting of HIF-1alpha and beta subunits. The activities of HIF-1 is mainly determined by HIF-1alpha, which transcriptional activity and DNA-binding ability were strictly regulated by O2 concentration, and other stimuli such as metalion, nitric oxide(NO), reactive oxygen species (ROS), and many growth factors. Here we reviewed the mechanisms of regulation of HIF-1alpha expression.

Animals↗