ABSTRACT
Objective: To clone the key enzyme gene involved in the biosynthesis of esculentoside A(EsA),acetoacetyl-CoA transferase(AACT) gene was cloned from Phytolacca americana for bioinformatics analysis and prokaryotic expression. Method: Total RNA was extracted from the root of P. americana, and then cDNA was synthesized through the reverse transcription. Based on analysis of the transcriptome data of P. americana, the specific primers of PaAACT gene were designed,and the cDNA sequence of PaAACT gene was amplified by polymerase chain reaction(PCR) method. Prokaryotic induction,expression and purification of the target protein were induced through the construction of the prokaryotic expression vector pET-32a-PaAACT. Result: The open reading frame (ORF) of PaAACT gene was 1 254 bp,and encoded 417 amino acid residues. Bioinformatic analysis showed that the molecular formula of PaAACT protein was C1 914H3 120N538O576S17,inferring that its molecular weight was 43.43 kDa,the theoretical isoelectric point was 8.90,and the instability index of PaAACT protein was 32.27,which was a stable protein. According to bioinformatics analysis,PaAACT protein was a member of the thiolase family and contained one conserved site and one active site of the thiolase family at the C-terminal. PaAACT protein may be located in the cytoplasm,without a signal peptide or transmembrane domain. The phylogenetic analysis indicated that PaAACT protein showed the highest homology with AACT protein from polygonaceae plants (such as Beta vulgaris). The recombinant PaAACT protein was successfully expressed in Escherichia coli BL21(DE3) strain through IPTG induction, and the purified target protein was obtained by Ni2+ affinity chromatography. Conclusion: In this study,the PaAACT gene was cloned from P. americana,which lays a foundation for further determination of enzyme activity assay of PaAACT and preparation of antibody,and provides the theoretical basis for studying its role in the biosynthesis pathway of EsA.