Unsaturated rhamnogalacturonyl hydrolase (EC 3.2.1.172, YteR, YesR) is an enzyme with systematic name 2-O-(4-deoxy-beta-L-threo-hex-4-enopyranuronosyl)-alpha-L-rhamnopyranose hydrolase. This enzyme catalyses the following chemical reaction2-O-(4-deoxy-beta-L-threo-hex-4-enopyranuronosyl)-alpha-L-rhamnopyranose + H2O 5-dehydro-4-deoxy-D-glucuronate + L-rhamnopyranose