A stromal glutamyl endopeptidase (GEP) that can cleave in vitro a short peptide corresponding to the N-terminal part of Lhcb1 (which belongs to the family of chlorophyll a/b binding proteins) was recently found in pea. Not all Glutamyl endopeptidase belong to Alpha/beta Hydrolases ( see glutamic-class prolyl-endopeptidase neprosin). Glutamyl endopeptidase cleaves the synthetic substrate Z-Leu-Leu-Glu-naphthylamide (Yamauchi et al., 2001).
Two protease activities of pea chloroplasts, one located in the stroma and the other associated to the thylakoid membrane, are described. Both proteases catalyse the endo-proteolytic cleavage of a peptide corresponding to the N-terminal loop and the first turn in helix-B of light-harvesting complex II (Lhcb1 from pea). The stromal protease cleaves preferentially on the carboxy-side of glutamic acid residues. Inhibitor studies indicate that this protease is a serine-type protease. The protease was partially purified and could be correlated to a 95-kDa polypeptide band on SDS-polyacrylamide gels. The 95 kDa protein was partially sequenced and showed similarity to an to an unknown protein from A. thaliana (in the NCBI public database) as well as to a glutamyl endopeptidase purified from crude extract of cucumber leaves. It is concluded that the stromal protease is a chloroplast glutamyl endopeptidase (cGEP). The protease localized in the thylakoid membrane, cleaved the peptide at only one site, close to its N terminus. The activity of the thylakoid-associated protease was found to be drastically increased in the presence of the reducing agent 1,4-dithiothreitol. Inhibitor studies suggest that this protease is a cysteine- or serine-type protease. The possible roles of these proteases in the regulation of photosynthetic electron transport and in the chloroplast homeostasis are discussed.
We purified a glutamyl endopeptidase that is a major foliar endopeptidase in cucumber. The endopeptidase had a molecular mass of 400 kDa, consisted of four subunits of 97 kDa, and was inactivated by SH-modifying reagents. Its optimum pH and optimum temperature were 8.0 and 30-37 degrees C, respectively. An internal amino acid sequence of the endopeptidase was highly homologous to a partial sequence of unidentified proteins deduced from genetic information for Arabidopsis thaliana, soybean and rice, but not to the sequences of bacterial glutamyl endopeptidases or animal proteases. Therefore, the unidentified proteins might be glutamyl endopeptidases and be widely distributed only among plant species. The activity of the cucumber glutamyl endopeptidase was inhibited by at least three inhibitors existing in cucumber leaves. One of the inhibitors was a competitive inhibitor of 25 kDa, which did not significantly inhibit commercial endopeptidases derived from animals and microorganisms. This suggests that the cucumber glutamyl endopeptidase might be controlled by endogenous inhibitors in vivo.
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No structure scheme yet for this family
No Structure yet in this family
Genes Proteins in Glutamyl_Peptidase_S9 family (370)
Fragments of genes in Glutamyl_Peptidase_S9 family (17)
