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Publication Abstract from PubMed

Enzyme-catalyzed beta-elimination of sugar uronic acids, exemplified by the degradation of plant cell wall pectins, plays an important role in a wide spectrum of biological processes ranging from the recycling of plant biomass through to pathogen virulence. The three-dimensional crystal structure of the catalytic module of a "family PL-10" polysaccharide lyase, Pel10Acm from Cellvibrio japonicus, solved at a resolution of 1.3 A, reveals a new polysaccharide lyase fold and is the first example of a polygalacturonic acid lyase that does not exhibit the "parallel beta-helix" topology. The "Michaelis" complex of an inactive mutant in association with the substrate trigalacturonate/Ca2+ reveals the catalytic machinery harnessed by this polygalacturonate lyase, which displays a stunning resemblance, presumably through convergent evolution, to the tetragalacturonic acid complex observed for a structurally unrelated polygalacturonate lyase from family PL-1. Common coordination of the -1 and +1 subsite saccharide carboxylate groups by a protein-liganded Ca2+ ion, the positioning of an arginine catalytic base in close proximity to the alpha-carbon hydrogen and numerous other conserved enzyme-substrate interactions, considered in light of mutagenesis data for both families, suggest a generic polysaccharide anti-beta-elimination mechanism.

Convergent evolution sheds light on the anti-beta -elimination mechanism common to family 1 and 10 polysaccharide lyases.,Charnock SJ, Brown IE, Turkenburg JP, Black GW, Davies GJ Proc Natl Acad Sci U S A. 2002 Sep 17;99(19):12067-72. Epub 2002 Sep 9. PMID:12221284^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.