Recombinant expression and secretion of mpd gene using the promoters and signal peptide-encoding sequences of ytkA and ywoF gene from Bacillus subtilis / 生物工程学报

A shuttle promoter-probe vector pNW33N-mpd was constructed with the E. coli-B. subtilis shuttle vector pNW33N and the mature mpd gene without it' s signal peptide-encoding sequence. The promoter fragments of B. subtilis ytkA and ywoF gene were cloned from plasmid pMPDP3 and pMPDP29 then generated the shuttle expression vector pNYTM and pNYWM. Expression vectors pNYTM and pNYWM were transformed into B. subtilis 1A751 to construct the expression strain 1A751 (pNYTM) and 1A751 (pNYTM), in these strains, under the control of the promoters and signal peptides of ytkA and ywoF gene, mpd gene was expressed and secreted with its biological activity; the result showed that the promoter of ytkA gene is much stronger than that of ywoF gene. Then a new shuttle expression-secretion vector pYNMK was constructed using the ytkA gene promoter and the signal peptide-encoding sequence of B. subtilis nprB gene, the expression of mpd gene achieved a higher level using the B. subtilis WB800 as the host, the methyl parathion hydrolase activity accumulated to a maximum level of 10.40 u/mL after 84 h of cultivation at the late stationary phase, which was 10.8-fold higher than the expression level of the original Plesiomonas strain M6, about 91.4% of the recombinant expression production was secreted into the culture medium.

Determination of the catalytic structures of methyl parathion hydrolase / 生物工程学报

Methyl parathion hydrolase (MPH) is a novel member of organophosphorus hydrolase. In this study, mpd gene was expressed in Escherichia coli DH5alpha with its native promoter. MPH was purified to homogeneity. Results show that metal-chelating compounds cannot inhabit the enzyme activity. Inductively Coupled Plasma-Atomic Emission Spectrometry analysis showed that MPH is a zinc-containing enzyme, the Zinc to enzyme molar ratio is near 2:1. In order to investigate critical residues related to enzymatic activity of MPH, chemical modification reagents EDC, DEPC, butanedione and pyridoxal were tested. Experiment results suggested that aspartate, glutamate, arginine and lysine are not important for enzyme activity. But DEPC, which can modify histidine residue, inactivate the enzyme activity greatly, and the inactivation rate is 9.6 h(-1). This result reflects that histidine residues are essential for enzyme activity. All these results provide basic data for MPH structure and molecular evolution research.

Isolation and Characterization of a Temperature-sensitive p-Nitrophenol Degradation Related Genes Mutant Strain / 微生物学通报

A temperature-sensitive mutant strain was isolated after transposon mutagenesis with Tn5 and named MT54.PCR was carried out with primers designed according to the sequence of transposon,the PCR products showed that the MT54 carried transposon in the genome. The mutant grew well at 30℃in minimal medium(MM)containing p-nitrophenol(PNP)as sole carbon source,while it cannot grow at 37℃in the same medium,NO_2.detection results also proved that.Comparing the degradation rate of PNP and hydroquinone of MT54 and DLL-E4 at different temperature,it was speculated that the mutant site locate in the PNP degradation related genes.

ENZYMOLOGY OF MICROBIAL DEGRADATION OF ORGANOPHOSPHATE CHEMICALS / 微生物学通报

Organophosphate chemicals are widely used as agricultural pesticides and war reagents, their biodegradation is emphasized on the theoretical and practical aspects. Organophosphate hydrolases play important roles in the biodegradation of organophosphate chemicals. Great advancement was achieved recently in the determination of crystal structure and catalytic mechanisms of the hydrolase. This paper reviewed the research progresses in the enzymology, protein structure, catalytic mechanisms and application of the organophosphate hydrolase, and predicted the future research in this field.