Guojun Zheng

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A novel (+)-γ-lactamase used for the resolution of racemic γ-lactam from Bradyrhizobium japonicum USDA 6 was found as a result of sequence-structure guided genome mining. It consists of 409 amino acids, only 49% of which are identical to the amino acid sequences of the known (+)-γ-lactamase from Sulfolobus solfataricus. This is only the third(More)
A (−) gamma-lactamase fromMicrobacterium hydrocarbonoxydans was purified to homogeneity by chromatography methods. SDS-PAGE showed the molecular weight of the enzyme was about 31 kDa. The purified enzyme had a specific activity of 61.3±2.5 U mg−1 for 2-azabicyclo [2.2.1] hept-5-en-3-one [(−) gamma-lactam]. The enantioselectivity factor (E) of the purified(More)
Using immobilized cells of a novel strain of Microbacterium hydrocarbonoxydans L29-9 in polymers of polyvinyl alcohol (PVA)-alginate-boric acid, enantioselective resolution of racemic γ-lactam to produce (-)γ-lactam was successfully carried out. A 6:1 ratio of PVA:sodium alginate not only prevented agglomeration of the matrix but also produced beads with(More)
5-Methyluridine has been synthesized in high yield using guanosine and thymine as starting materials in the presence of highly thermostable recombinant purine nucleoside phosphorylase (PNP) and uridine phosphorylase (UP) obtained from hyperthermophilic aerobic crenarchaeon Aeropyrum pernix. Key reaction parameters such as pH, temperature, concentration of(More)
A thermostable formamidase from the hyperthermophilic archaeon Sulfolobus solfataricus P2 was revealed to be a novel, thermostable (+)-γ-lactamase. This (+)-γ-lactamase (Sso2810) is composed of only 318 amino acid residues, in contrast to a previously reported (+)-γ-lactamase (Sso2122) with 504 amino acid residues from the same strain. Herein, we(More)
The enantiomers of 2-azabicyclo[2.2.1]hept-5-en-3-one (γ-lactam) are key chiral synthons in the synthesis of antiviral drugs such as carbovir and abacavir. (+)-γ-Lactamase can be used as a catalyst in the enzymatic preparation of optically pure (-)-γ-lactam. Here, a (+)-γ-lactamase discovered from Bradyrhizobium japonicum USDA 6 by sequence-structure guided(More)
A thermostable formamidase from the aerobic hyperthermophilic archaeon Aeropyrum pernix was revealed a novel type II (+)-γ-lactamase. This type II (+)-γ-lactamase is only composed of 377 amino acid residues, in contrast to another thermostable (+)-γ-lactamase from Sulfolobus solfataricus with 504 amino acid residues (type I). It is interesting that there(More)
A (−)γ-lactamase, Mhg, from Microbacterium hydrocarbonoxydans was over-expressed in E. coli and was characterized after purification. The maximum activity was at pH 8.0 and 60°C and the half life of Mhg was ~30 min at 75°C. The enzyme was activated by DTT. The catalytic triad of the (−)γ-lactamase is comprised of residues Ser98, Asp230, and His259 and an(More)
Biocatalyzed synthesis of nucleoside analogues was carried out using two thermostable nucleoside phosphorylases from the hyperthermophilic aerobic crenarchaeon Aeropyrum pernix K1. The synthesis of the 2,6-diaminopurine nucleoside and 5-methyluridine was used as a reaction model to test the process. Both the purine nucleoside phosphorylase (apPNP) and(More)
Five truncated constructs of Xcc_est GDSL esterase from Xanthomonas campestris were heterologously expressed and purified. The truncated constructs with a RGD motif had higher specific activities than those without the motif. The specific activity of wild-type Xcc_est was 32.5 ± 2.7 U/mg, while the RGD mutant was 12.5 ± 4.9 U/mg. Moreover, we expressed(More)