Abstract Bacterial sulfatases can be good tools to increase the molecular diversity of glycosaminoglycan synthetic fragments. A chondroitin 4-O-sulfatase from the human commensal bacterium Bacteroides thetaiotaomicron has recently been identified and expressed. In order to use this enzyme for synthetic purposes, the minimal structure required for its activity has been determined. For that, four 4-O-sulfated monosaccharides and one 4-O-sulfated disaccharide have been synthesized and used as substrates with the sulfatase. The minimum structure was shown to be a disaccharide but in contrast to the natural substrate, which must have a 4,5-insaturation, the enzyme accepts as substrate, a disaccharide with a saturated glucuronic acid at the non-reducing end and even a glucopyranosyl moiety without the carboxylic acid functionality.