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Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK
Correspondence
Nicola D. Walker
Nicola.Walker{at}agresearch.co.nz
Ruminal bacteria of the genus Prevotella play a crucial role in peptide breakdown in the rumen, a component of protein catabolism that leads to the inefficient use of dietary protein by ruminant animals. This is the first report of the cloning of a peptidase gene from a ruminal bacterium. Part of the dipeptidyl peptidase type IV (DPP-IV) gene from Prevotella albensis M384T was cloned using degenerate primers designed from conserved regions found within other known DPP-IV sequences. Flanking regions were determined by genomic walking. The DPP-IV gene was expressed in Escherichia coli. The cloned enzyme required a free N terminus and catalysed the removal of X-Pro dipeptide from proline-containing oligopeptides, where proline was the second residue from the N terminus. It was inhibited by serine protease inhibitors and the substrate analogue for mammalian DPP-IV, diprotin A. The properties of the cloned enzyme were similar to those of the native form in P. albensis and, in general, DPP-IVs from other organisms. The enzyme contained a conserved motif which is associated with the S9 class of prolyl oligopeptidases. The DPP-IV gene appeared not to be part of a contiguous operon. Regions with similarity to other putative promoters of Prevotella spp. were also identified. Construction of a phylogenetic tree demonstrated that the DPP-IV of P. albensis clusters with other DPP-IVs found in bacteria of the CytophagaFlexibacterBacteroidaceae (CFB) phylum, which are more closely related to eukaryotic DPP-IVs than the DPP-IV-like enzyme (PepX) of the lactic acid bacteria.
The GenBank accession number for the Prevotella albensis dipeptidyl peptidase type IV (DPP-IV) sequence reported in this article is AJ310187.
Present address: AgResearch Ltd, Grasslands, Private Bag 11008, Palmerston North, New Zealand.
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