Cloning, prokaryotic expression and characterization of lysine decarboxylase gene from Huperzia serrata / 生物工程学报

Huperzine A is a promising drug to treat Alzheimer's disease (AD). To date, its biosynthetic pathway is still unknown. Lysine decarboxylase (LDC) has been proposed to catalyze the first-step of the biosynthesis of huperzine A. To identify and characterize LDCs from Huperzia serrata, we isolated two LDC fragments (LDC1 and LDC2) from leaves of H. serrata by RT-PCR and then cloned them into pMD 19-T vector. Sequence analysis showed that LDC1 and LDC2 genes shared 95.3% identity and encoded the protein of 212 and 202 amino acid residues respectively. Thus, we ligated LDC genes into pET-32a(+) to obtain recombinant expressing vectors pET-32a(+)/LDC1 and pET-32a(+)/LDC2 respectively. We further introduced two expression vectors into Escherichia coli BL21(DE3) and cultured positive colonies of E. coli in liquid LB medium. After inducing for 4 hours with 260 μg/mL IPTG at 30 degrees C, soluble recombinant Trx-LDC1 and Trx-LDC2 were obtained and isolated for purification using a Ni-NTA affinity chromatography. We incubated purified recombinant proteins with L-lysine in the enzyme reaction buffer at 37 degrees C and then derived the reaction products using dansyl chloride. It was found that both Trx-LDC1 and Trx-LDC2 had decarboxylase activity, could convert L-lysine into cadaverine by way of thin layer chromatography assay. Further, bioinformatics analysis indicated that deduced LDC1 and LDC2 had different physicochemical properties, but similar secondary and three-dimensional structures.

Tube feeding with the mixture Of anisodamine and aluminium hydroxide gel to prevent and cure the upper digestive tract ulcer bleeding resulted from severe brain damage / 中华消化内镜杂志

Objective To study the effect of early administration of a mixture of Anisodamine and A-luminium hydroxide gel via nasal gastric tube in preventing in stress - induced digestive tract bleeding in patients with severe brain damage. Method One thousand one hundred and thirteen patients with severe brain damage were divided into three groups: control group 410 cases without any measures to prevent digestive tract bleeding within 72 hours after injury, treatment group A 540 cases when given cimetidine, ranitidine and Losec by intravenous injection or nasal feeding. Group B 240 cases who received nasal feeding of aniso-damine and Aluminium Hydroxide gel mixture. The incidence of bleeding in each group was recorded . Results The incidence of the upper digestive tract bleeding in group B is 1.25% , compared with that of control group( x2 = 90. 13, P