title: Characterization of a unique proline iminopeptidase from white-rot basidiomycetes Phanerochaete chrysosporium.
abstract: A putative gene encoding proline iminopeptidase (PchPiPA) was cloned from Phanerochaete chrysosporium BKM-F-1767 by RT-PCR and expressed successfully in Escherichia coli. The cDNA is 942 bp in length and encodes 313 amino acids. The recombinant enzyme was only able to hydrolyze Pro-pNA among the tested synthetic substrates. There is no activity detected toward Leu-pNA, Phe-pNA and Tyr-pNA, as well as GGG-pNA, SGR-pNA, AAV-pNA, AAPL-pNA, AAVA-pNA. And the recombinant enzyme could cleave the peptides derived from enzyme-hydrolytic natural proteins to release free lysine, which was confirmed using synthetic oligopeptides with lysine at N termini as substrate. The optimal pH and temperature for this enzyme were 8.0 and 45 degrees C, respectively. The catalytic activity was inhibited slightly by Mg(2+), Al(3+), Ca(2+), Fe(3+), Fe(2+) and Ba(2+); strongly by Ni(2+), Mn(2+) and Co(2+), and almost inactivated by Zn(2+), Cu(2+) and Hg(2+). In addition, the enzyme was not sensitive to EDTA-Na(2), as well as redoxes of DTT, beta-ME and H(2)O(2). The protease inhibitors of benzamidine hydrochloride and phenylmethyl sulfonyfluoride caused a moderate inhibition. The V(max), K(m) and k(cat) toward Pro-pNA were 347.86 mumol min(-1) mg(-1), 2.15 mM and 218.10 S(-1), respectively. The deduced catalytic triad of Ser(107), Asp(264) and His(292) was confirmed by site-directed mutagenesis because the individual replacement of Ser(107) to Asp, Asp(264) to Ala or His(292) to Leu led complete inactivation. Transcriptional analysis by RT-PCR showed that PchPiPA could be expressed under ligninolytic and non-ligninolytic conditions. Conclusively, it was suggested that the proline iminopeptidase may be a member of the proteolytic system in this fungus. The availability of recombinant protein may be potentially used in certain proteolytic processing.
authors.affiliation: Ministry of Education Key Laboratory for Bio-resources and Eco-environment, Sichuan Key Laboratory of Molecular Biology and Biotechnology, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610064, PR China.
authors.forename: Nian
authors.initials: N
authors.lastname: Li
authors.forename: Jin-Ming
authors.initials: JM
authors.lastname: Wu
authors.forename: Lin-Feng
authors.initials: LF
authors.lastname: Zhang
authors.forename: Yi-Zheng
authors.initials: YZ
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Feng
mesh_terms: D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D055162:Biocatalysis; D003001:Cloning, Molecular; D004795:Enzyme Stability; D005511:Food Handling; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis / Q000187:drug effects; D007700:Kinetics; D008670:Metals / Q000494:pharmacology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000378:metabolism; D020075:Phanerochaete / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D008670:Metals; D010455:Peptides; D000626:Aminopeptidases; C022450:prolyl aminopeptidase