Document Detail

Nepenthesin, a unique member of a novel subfamily of aspartic proteinases: enzymatic and structural characteristics.
MedLine Citation:
PMID:  16381601     Owner:  NLM     Status:  MEDLINE    
Carnivorous plants are known to secrete acid proteinases to digest prey, mainly insects, for nitrogen uptake. In our recent study, we have purified, for the first time, to homogeneity two acid proteinases, nepenthesin I (Nep I) and nepenthesin II (Nep II) from the pitcher fluid of Nepenthes distillatoria and investigated their enzymatic and structural characteristics. Both enzymes were optimally active at pH approx. 2.6 toward acid-denatured hemoglobin; the specificity of Nep I toward oxidized insulin B chain appears to be similar, but slightly wider than those of other aspartic proteinases (APs). At or below 50 degrees C both enzymes were remarkably stable; especially Nep I was extremely stable over a wide range of pH from 3 to 10 for over 30 days. This suggests an evolutionary adaptation of the enzymes to their specific habitat. We have also cloned the cDNAs and deduced the complete amino acid sequences of the precursors of Nep I and Nep II from the pitcher tissue of Nepenthes gracilis. Although the corresponding mature enzymes are homologous with ordinary pepsin-type APs, both enzymes had a high content of cysteine residues (12 residues per molecule), which are assumed to form six unique disulfide bonds as suggested by computer modeling and are thought to contribute toward the remarkable stability of Neps. Moreover, the amino acid sequence identity of Neps with ordinary APs, including plant vacuolar APs, are remarkably low (approx. 20%), and phylogenetic comparison shows that Neps are distantly related to them to form a novel subfamily of APs with a high content of cysteine residues and a characteristic insertion, named 'the Nep-type AP (NAP)-specific insertion', including a large number of novel, orthologous plant APs emerging in the gene/protein databases.
Kenji Takahashi; Senarath B P Athauda; Koji Matsumoto; Sanath Rajapakshe; Masayuki Kuribayashi; Masaki Kojima; Nobuko Kubomura-Yoshida; Akihiro Iwamatsu; Chiaki Shibata; Hideshi Inoue
Publication Detail:
Type:  Journal Article; Review    
Journal Detail:
Title:  Current protein & peptide science     Volume:  6     ISSN:  1389-2037     ISO Abbreviation:  Curr. Protein Pept. Sci.     Publication Date:  2005 Dec 
Date Detail:
Created Date:  2005-12-29     Completed Date:  2006-02-06     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  100960529     Medline TA:  Curr Protein Pept Sci     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  513-25     Citation Subset:  IM    
Laboratory of Molecular Biochemistry, School of Life Science, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan.
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MeSH Terms
Amino Acid Sequence
Angiosperms / enzymology
Aspartic Acid Endopeptidases / chemistry*,  genetics,  metabolism*
Crystallography, X-Ray
Hydrogen-Ion Concentration
Models, Molecular
Molecular Sequence Data
Protein Structure, Tertiary
Substrate Specificity
Reg. No./Substance:
EC 3.4.23.-/Aspartic Acid Endopeptidases

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