Cloning and Sequencing of the Histidine Decarboxylase Gene from Photobacterium phosphoreum and its Functional Expression in Escherichia coli

Abstract

The major causative agent of scombroid poisoning is histamine formed by bacterial decarboxylation of histidine. We reported previously that histamine was exclusively formed by the psychrotrophic halophilic bacteria Photobacterium phosphoreum in scombroid fish during storage at or below 10 degrees C. Moreover, histamine-forming ability was affected by two histidine decarboxylases (HDCs): constitutive and inducible enzymes. In this study, the gene encoding P. phosphoreum HDC was cloned into Escherichia coli and sequenced. A sequence analysis of the DNA corresponding to the hdc gene revealed an open reading frame of 1,140 bp coding for a pyridoxal-5'-phosphate-dependent HDC of 380 amino acid residues with a predicted molecular mass of 42.6 kDa. The HDC amino acid sequences formed a phylogenetic clade with strong bootstrap support and revealed high sequence similarities among the P. phosphoreum isolate and species of the family Enterobacteriaceae and a separate phylogenetic branch with the lowest sequence similarity between the isolate and the taxonomically closer Listonella anguillarum. The T7 promoter was used to overexpress the hdc gene in E. coli cells. The recombinant clone, E. coli BL21(DE3), displayed significant levels of HDC activity. The recombinant hdc gene was suggested to code the inducible HDC; therefore, the optimum reaction conditions of the recombinant HDC were similar to those of the inducible HDC in the P. phosphoreum isolate. In addition, a putative catabolite-repressor protein binding site, amino acid permease gene, and histidine-tRNA synthetase gene were found in flanking regions of the hdc gene.

Induction of the histidine decarboxylase genes ofPhotobacterium damselaesubsp.damselae(formallyP. histaminum) at low pH

“…1986; Kamath et al. 1991); P. phosphoreum (80·2%, Morii et al. 2006); and P. damsela e (100%, Kanki et al.…”

“…However, the reason for transcription of these hdc genes as either bi‐ or mono‐cistronic messages remains to be elucidated. Morii and Kasama (1995, 2004) and Morii et al. (2006) reported that the decarboxylation of histidine by P. phosphoreum was achieved by two types of histidine decarboxylase enzymes (constitutive and inducible), which could be separated and fractionated by gel chromatography.…”

“…We isolated and sequenced the histidine decarboxylase gene (hdcA), which showed high identity with the amino acid sequences of histidine decarboxylases of other known Gram-negative bacteria: M. morganii (79AE6% identity), R. planticola (79AE1%), and E. aerogenes (76AE9%) (Vaaler et al 1986;Kamath et al 1991); P. phosphoreum (80AE2%, Morii et al 2006); and P. damselae (100%, Kanki et al 2007) (Fig. 3).…”

“…1986) , Raoultella planticola (formally named Klebsiela ) , Enterobacter aerogenes (Kamath et al. 1991) and Photobacterium phosphoreum (Morii et al. 2006).…”

“…While histidine decarboxylases from Gram-positive bacteria are pyruvoyl-dependent enzymes, those from Gram-negative bacteria are pyridoxyal-P-dependent enzymes. The amino acid sequence of pyridoxal 5¢-phosphate dependent histidine decarboxylase has been studied in four bacterial species: Morganella morgani (Vaaler et al 1986), Raoultella planticola (formally named Klebsiela), Enterobacter aerogenes (Kamath et al 1991) and Photobacterium phosphoreum (Morii et al 2006). However, transcriptional analysis of these enzymes under acidic conditions has not yet been carried out.…”