Prolyl Endopeptidase fromSphingomonas capsulata:Isolation and Characterization of the Enzyme and Nucleotide Sequence of the Gene

Prolyl endopeptidase (prolyl oligopeptidase, EC 3.4.21.26) was purified fromSphingomonas capsulataIFO 12533, and its gene was cloned and expressed inEscherichia coli.The recombinant enzyme was markedly inhibited by diisopropyl phosphofluoridate and hardly affected by SH reagents or metal chelators, similar to the native enzyme purified fromS. capsulata.Nucleotide sequencing analysis revealed an open reading frame of 2169 bp, coding for a protein of 723 amino acids with a predicted molecular weight of 78,433. The amino acid sequence was 39.6, 45.3, 38.9, and 38.3% homologous toFlavobacterium meningosepticum, Aeromonas hydrophila,porcine brain, and human T cell prolyl endopeptidase, respectively. A region near the C-terminus and the region containing the putative catalytic triad residues were highly conserved. The enzyme was crystallized by the hanging drop vapor diffusion method, using ammonium sulfate as a precipitant.