Isolation and characterization of the glutaminyl cyclases from Solanum tuberosum and Arabidopsis thaliana: implications for physiological functions.
Biol Chem
; 388(2): 145-53, 2007 Feb.
Article
em En
| MEDLINE
| ID: mdl-17261077
ABSTRACT
Glutaminyl cyclases (QCs) catalyze the formation of pyroglutamic acid at the N-terminus of several peptides and proteins. On the basis of the amino acid sequence of Carica papaya QC, we identified cDNAs of the putative counterparts from Solanum tuberosum and Arabidopsis thaliana. Upon expression of the corresponding cDNAs from both plants via the secretory pathway of Pichia pastoris, two active QC proteins were isolated. The specificity of the purified proteins was assessed using various substrates with different amino acid composition and length. Highest specificities were observed with substrates possessing large hydrophobic residues adjacent to the N-terminal glutamine and for fluorogenic dipeptide surrogates. However, compared to Carica papaya QC, the specificity constants were approximately one order of magnitude lower for most of the QC substrates analyzed. The QCs also catalyzed the conversion of N-terminal glutamic acid to pyroglutamic acid, but with approximately 10(5)- to 10(6)-fold lower specificity. The ubiquitous distribution of plant QCs prompted a search for potential substrates in plants. Based on database entries, numerous proteins, e.g., pathogenesis-related proteins, were found that carry a pyroglutamate residue at the N-terminus, suggesting QC involvement. The putative relevance of QCs and pyroglutamic acid for plant defense reactions is discussed.
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Base de dados:
MEDLINE
Assunto principal:
Solanum tuberosum
/
Arabidopsis
/
Aminoaciltransferases
Tipo de estudo:
Diagnostic_studies
Idioma:
En
Revista:
Biol Chem
Ano de publicação:
2007
Tipo de documento:
Article
País de afiliação:
Alemanha