Affiliation:
1. Laboratoire de Génétique Moléculaire des Microorganismes et des Interactions Cellulaires, UMR-CNRS 5577, INSA, F-69621 Villeurbanne Cedex, France
Abstract
ABSTRACT
Erwinia chrysanthemi
3937 secretes into the external medium several pectinolytic enzymes, among which are eight isoenzymes of the endo-cleaving pectate lyases: PelA, PelB, PelC, PelD, and PelE (family 1); PelI (family 4); PelL (family 3); and PelZ (family 5). In addition, one exo-cleaving pectate lyase, PelX (family 3), has been found in the periplasm of
E. chrysanthemi
. The
E. chrysanthemi
3937 gene
kdgC
has been shown to exhibit a high degree of similarity to the genes
pelY
of
Yersinia pseudotuberculosis
and
pelB
of
Erwinia carotovora
, which encode family 2 pectate lyases. However, no pectinolytic activity has been assigned to the KdgC protein. After verification of the corresponding nucleotide sequence, we cloned a longer DNA fragment and showed that this gene encodes a 553-amino-acid protein exhibiting an exo-cleaving pectate lyase activity. Thus, the
kdgC
gene was renamed
pelW
. PelW catalyzes the formation of unsaturated digalacturonates from polygalacturonate or short oligogalacturonates. PelW is located in the bacterial cytoplasm. In this compartment, PelW action could complete the degradation of pectic oligomers that was initiated by the extracellular or periplasmic pectinases and precede the action of the cytoplasmic oligogalacturonate lyase, Ogl. Both cytoplasmic pectinases, PelW and Ogl, seem to act in sequence during oligogalacturonate depolymerization, since oligomers longer than dimers are very poor substrates for Ogl but are good substrates for PelW. The estimated number of binding subsites for PelW is three, extending from subsite −2 to +1, while it is probably two for Ogl, extending from subsite −1 to +1. The activities of the two cytoplasmic lyases, PelW and Ogl, are dependent on the presence of divalent cations, since both enzymes are inhibited by EDTA. In contrast to the extracellular pectate lyases, Ca
2+
is unable to restore the activity of PelW or Ogl, while several other cations, including Co
2+
, Mn
2+
, and Ni
2+
, can activate both cytoplasmic lyases.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
71 articles.
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