Abstract
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 Angstrom, 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 a-carbon hydrogen and numerous other conserved enzyme-substrate interactions, considered in light of mutagenesis data for both families, suggest a generic polysaccharicle anti-beta-elimination mechanism.
| Original language | English |
|---|---|
| Pages (from-to) | 12067-12072 |
| Number of pages | 6 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 99 |
| Issue number | 19 |
| DOIs | |
| Publication status | Published - 17 Sept 2002 |
Keywords
- CARBOHYDRATE-ACTIVE ENZYMES
- PECTATE LYASE
- PSEUDOMONAS-CELLULOSA
- 3-DIMENSIONAL STRUCTURE
- ERWINIA-CHRYSANTHEMI
- CARBOXYLIC-ACIDS
- ALPHA-PROTONS
- BINDING
- SITE
- INTERMEDIATE