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Journal of Bacteriology, June 1999, p. 3705-3709, Vol. 181, No. 12
Molecular Genetics of Industrial
Micro-organisms, Wageningen Agricultural University, 6703 HA
Wageningen, The Netherlands,1 and
Laboratoire de Génétique Moléculaire des
Micro-organismes et des Interactions Cellulaires, UMR-CNRS 5577, INSA, 69 621 Villeurbanne Cedex, France2
Received 23 November 1998/Accepted 17 April 1999
Five endopectate lyases from the phytopathogenic bacterium
Erwinia chrysanthemi, PelA, PelB, PelD, PelI, and PelL,
were analyzed with respect to their modes of action on polymeric and
oligomeric substrates (degree of polymerization, 2 to 8). On
polygalacturonate, PelB showed higher reaction rates than PelD, PelI,
and PelA, whereas the reaction rates for PelL were extremely low. The
product progression during polygalacturonate cleavage showed a typical
depolymerization profile for each enzyme and demonstrated their
endolytic character. PelA, PelI, and PelL released oligogalacturonates
of different sizes, whereas PelD and PelB released mostly unsaturated
dimer and unsaturated trimer, respectively. Upon prolonged incubation, all enzymes degraded the primary products further, to unsaturated dimer
and trimer, except for PelL, which degraded the primary products to
unsaturated tetramer and pentamer in addition to unsaturated dimer and
trimer. The bond cleavage frequencies on oligogalacturonates revealed
differences in the modes of action of these enzymes that were
commensurate with the product progression profiles. The preferential products formed from the oligogalacturonates were unsaturated dimer for
PelD, unsaturated trimer for PelB, and unsaturated tetramer for PelI
and PelL. For PelA, preferential products were dependent on the sizes
of the oligogalacturonates. Whereas PelB and PelD displayed their
highest activities on hexagalacturonate and tetragalacturonate, respectively, PelA, PelI, and PelL were most active on the octamer, the
largest substrate used. The bond cleavage frequencies and reaction
rates were used to estimate the number of subsites of each enzyme.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Modes of Action of Five Different Endopectate
Lyases from Erwinia chrysanthemi 3937
*
Corresponding author. Mailing address: Molecular
Genetics of Industrial Micro-organisms, Wageningen Agricultural
University, Dreijenlaan 2, 6703 HA Wageningen, The Netherlands. Phone:
31 317484439. Fax: 31 317484011. E-mail:
jac.benen{at}algemeen.mgim.wau.nl.
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