Rhamnogalacturonan exolyase (, YesX) is an enzyme with systematic name ñ-<small>L</small>-rhamnopyranosyl-(1âÂÂ4)-ñ-<small>D</small>-galactopyranosyluronate exolyase. This enzyme catalyses the following chemical reaction
Exotype eliminative cleavage of ñ-<small>L</small>-rhamnopyranosyl-(1âÂÂ4)-ñ-<small>D</small>-galactopyranosyluronic acid bonds of rhamnogalacturonan I oligosaccharides containing ñ-<small>L</small>-rhamnopyranose at the reducing end and 4-deoxy-4,5-unsaturated <small>D</small>-galactopyranosyluronic acid at the non-reducing end. The products are the disaccharide 2-O-(4-deoxy-ò-<small>L</small>-threo-hex-4-enopyranuronosyl)-ñ-<small>L</small>rhamnopyranose and the shortened rhamnogalacturonan oligosaccharide containing one 4-deoxy-4,5-unsaturated <small>D</small>-galactopyranosyluronic acid at the non-reducing end.
The enzyme is part of the degradation system for rhamnogalacturonan I in Bacillus subtilis strain 168.
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