Transcriptional expression and prokaryotic expression analysis of haloalkane dehalogenase gene from Gracilariopsis lemaneiformis

Haloalkane dehalogenase (HLD) is a kind of enzyme that can degrade halogenated aliphatic compounds. In order to provide information on the possible use of the algal HLD for the degradation of halogen compounds in the environment, we used bioinformatics, quantitative real-time PCR and pET28a system to study the characteristics and prokaryotic expression of HLD in the macroalga Gracilariopsis lemaneiformis (Rhodophyta). The open reading frame of HLD in G. lemaneiformis (recorded as GlHLD) was 969 bp, and its theoretical molecular weight and isoelectric point was approximately 36.33 ku and 5.53, respectively. The GlHLD amino acid sequence was identical with an HLD sequence of G. chorda (PXF45553.1), and was close to G. chorda and Chondrus crispus in the phylogenetic tree. The high temperature, substrate 1,2-dichloroethane and phytohormone salicylic acid all promoted the expression of GlHLD gene with an increment fold of 3.64, 2.64 and 2.43 times, respectively. Finally, the recombinant vector of pET28a-GlHLD was transformed into E. coli BL21 (DE3), and the recombinant protein displayed a dehalogenase activity. The optimal induction conditions were 16 °C and 0.1 mmol/L IPTG treatment for 12 h. And then, the HLD protein was preliminarily purified by nickel column. This study will lay the foundation for further understanding of the algal HLD family and the acquisition of high purity HLD enzyme.