Sandbox UNLPam 7

a-L-rhamnosidases (E.C. 3.2.1.40) are found widely distributed

in nature and have been reported in animals, plants, yeast, fungi and bacteria, where they are responsible for the cleavage of a-L-rhamnose from a wide range of compounds.1 a-L-rhamnose is found in plants and bacteria as components of polysaccharides, such as pectins,2 and the O antigen polysaccharides, responsible for determining the antigenicity of pathogenic bacteria3; it is also found in rhamnolipids4 and it is attached to small molecule natural products, such as rutin. There is industrial interest in arhamnosidases for use in the debittering of citrus juices and for the release of flavonoids from rhamnosylated precursors; in wine production they play a role in the hydrolysis of glycosylated terpene aroma compounds.

KoRha structure

The crystal structure of KoRha with rhamnose bound was determined to 2.7A ° resolution. The final model consisted of two KoRha subunits related by a non-crystallographic twofold axis (giving a corresponding solvent content of 73%) in the asymmetric unit, with each monomer containing a bound rhamnose. Dynamic light scattering had suggested that KoRha was a homodimer in solution and the structure of KoRha confirmed this, giving a dimer interface of 1389.9 A ° 2 (as calculated using the PISA server (http://www.ebi.ac. uk/pdbe/pisa/). Each monomer of KoRha is composed of two domains. Domain A, the catalytic domain, is mainly ahelical, consisting of residues 11–30 and 180–523, and contains the bound rhamnose. Domain B, the dimerization domain, is a b-sandwich domain consisting of residues 31–179.