Rhamnogalacturonan acetylesterase (RGAE) from Aspergillus aculeatus acts in synergy with rhamnogalacturonases on the enzymatic degradation of rhamnogalacturonan I (RG-I). RGAE is a member of the Carbohydrate Esterase Family 12 (CEF 12), which also includes two pectin acetylesterases, a cephalosporin C deacetylase and a number of bacterial proteins of unknown function. The proteins within this family are similar in sequence and are expected to share the same fold. The carbohydrate esterase family 12 has been shown to be a subfamily of a family of hydrolases described by Dalrymple et al. (1997). The proteins in this family are characterized by having three blocks of conserved sequence, but have little or no sequence similarity outside these blocks.