L-tyrosine is one of the 20 amino acids that make up proteins and is an essential amino acid for mammals, often used as a nutritional supplement. The conventional methods for synthesizing L-tyrosine have some problems such as the production of many by-products, high requirements for production conditions, and environmental pollution. In this study, we designed and constructed a multi-enzyme cascade for the synthesis of L-tyrosine with alanine, glutamate, ammonium chloride, and phenol as substrates. Initially, the sources of glutamate oxidase, alanine aminotransferase, and tyrosine phenol lyase were screened and analyzed, which was followed by the identification of the rate-limiting enzyme in the reaction process. A colorimetric screening method was established, and the rate-limiting enzyme DbAlaA was engineered to enhance its activity by 40.0%. Subsequently, the reaction conditions, including temperature, pH, cell concentration, and surfactant and coenzyme dosages, were optimized. After optimization, the yield of L-tyrosine reached 9.93 g/L, with a alanine conversion rate of 54.90%. Finally, a feed-batch fermentation strategy was adopted, and the yield of L-tyrosine reached 56.07 g/L after 24 h, with a alanine conversion rate of 65.22%. This study provides a reference for the whole-cell catalytic synthesis of L-tyrosine and its industrialization.
Tyrosine/biosynthesis* ; Escherichia coli/metabolism* ; Tyrosine Phenol-Lyase/genetics* ; Multienzyme Complexes/metabolism* ; Fermentation

OBJECTIVETo investigate the alteration of the gene HSD17B4 in esophageal squamous cell carcinoma and its potential significance.

METHODSThe mRNA expression and loss of heterozygosity (LOH) of HSD17B4 in 40 primary esophageal tumors were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and microsatellite analysis with the intragenic marker D5S1384 of the gene.

RESULTSThe frequencies of allelic loss of D5S1384 and the rate of down-regulation of gene HSD17B4 were 46.2% and 62.5%, respectively.

CONCLUSIONHSD17B4 may be a candidate tumor suppressor gene associated with esophageal squamous cell carcinoma.

17-Hydroxysteroid Dehydrogenases ; biosynthesis ; genetics ; Adult ; Aged ; Carcinoma, Squamous Cell ; genetics ; Down-Regulation ; Enoyl-CoA Hydratase ; biosynthesis ; genetics ; Esophageal Neoplasms ; genetics ; Female ; Gene Expression ; Gene Expression Regulation, Neoplastic ; genetics ; Genes, Tumor Suppressor ; Humans ; Hydro-Lyases ; Loss of Heterozygosity ; Male ; Microsatellite Repeats ; Middle Aged ; Multienzyme Complexes ; biosynthesis ; genetics ; Peroxisomal Multifunctional Protein-2 ; RNA, Messenger ; biosynthesis ; genetics ; Reverse Transcriptase Polymerase Chain Reaction

The enzyme complex 3b-hydroxysteroid dehydrogenase/delta(5)-delta(4)-isomerase (3beta-HSD) is involved in the biosynthesis of all classes of active steroids. The expression of 3beta-HSD in human uterine endometrium during the menstrual cycle and decidua was examined in an effort to understand its role during ova implantation. 3beta-HSD was weakly expressed in the glandular epithelium of the proliferative phase and moderately expressed in the glandular epithelium of secretory phase of the endometrium. In the decidua of the ectopic pregnancy, 3beta-HSD was strongly expressed. The human uterine endometrial 3beta-HSD was identified as being the same type as the placental 3beta-HSD by RT-PCR and sequence analysis. In addition to the expression of 3beta-HSD, P450scc was expressed in the decidua of the ectopic pregnancy. These results suggest that pregnenolone might be synthesized from cholesterol by P450scc de novo and then, it is converted to progesterone by 3beta-HSD in the uterine endometrium. The data implies that the endometrial 3beta-HSD can use not only the out-coming pregnenolone from the adrenal gland but also the self- made pregnenolone to produce progesterone. The de novo synthesis of progesterone in the endometrium might be a crucial factor for implantation and maintenance of pregnancy.
Cholesterol/chemistry ; Cholesterol Side-Chain Cleavage Enzyme/*biosynthesis/genetics ; Decidua/enzymology ; Endometrium/*enzymology ; Female ; Gene Expression/physiology ; Human ; Menstrual Cycle/physiology ; Multienzyme Complexes/*biosynthesis/genetics ; Placenta/enzymology ; Pregnancy ; Pregnenolone/biosynthesis ; Progesterone/biosynthesis ; Progesterone Reductase/*biosynthesis/genetics ; Steroid Isomerases/*biosynthesis/genetics

Genetic engineering on macrolide antibiotics was a new field in recent years and more than 100 novel polyketides had been produced until then. Using genomic DNA of S. erythraea A226 as a template, about 3.2 kb DNA fragment without KR6 domain was amplified by overlapping PCR technique and cloned into pWHM3 carrier, which resulted in the construction of homologous recombinant plasmid pWHM2201. Plasmid pWHM2201 was introduced into protoplasts of S. erythraea A226 by PEG-mediated transformation and integrated into the gene locus for erythromycin biosynthesis. After integrants grew for two generations on R3M media without Tsr, they were protoplasted and grown on R3M plates. By PCR identification, 8 mutants without KR6 domain were selected out and named S. erythraea M(1-8). With the identification of mass spectrometry, it was proved that S. erythraea M1 synthesized a novel ketolide compound 3-deoxy-3-oxo-erythronolide B.
Anti-Bacterial Agents ; biosynthesis ; chemistry ; Chromosomes, Bacterial ; Erythromycin ; analogs & derivatives ; biosynthesis ; chemistry ; Genetic Engineering ; Ketolides ; Molecular Structure ; Multienzyme Complexes ; genetics ; Saccharopolyspora ; enzymology ; genetics ; metabolism

Human calcitonin (hCT) is a 32 amino acid peptide hormone that requires C-terminal amidation for full biological activity. Calcitonin has important physiological function in vivo. We describe the couple expression of a synthesized modified human calcitonin(hmCT) gene fused with glutathione-S-transferase and rat peptidylglycine alpha-amidation monooxygenase (PAM) in insect cells infected by recombinant baculovirus GSTCT/PAM. Using Western blotting against hmCT or rat PAM, the GSThmCT fusion protein had been identified as well as the PAM. Following affinity chromatography with glutathione agarose column, the GSThmCT fusion protein produced by insect cells was purified. The purified fusion protein was also interacted with antibody against hmCT. The couple expression of a modification enzyme and its substrate in eucaryotic expression system may be used for producing other biological activity peptides.
Animals ; Baculoviridae ; genetics ; Calcitonin ; biosynthesis ; genetics ; Cells, Cultured ; Gene Expression ; Glutathione Transferase ; genetics ; Humans ; Insecta ; cytology ; Mixed Function Oxygenases ; biosynthesis ; genetics ; Multienzyme Complexes ; biosynthesis ; genetics ; Rats ; Recombinant Fusion Proteins ; genetics