Arylsulfatase B

Arylsulfatase B (ARSB) is an enzyme associated with mucopolysaccharidosis VI.

Arylsulfatase B is among a group of arylsulfatase enzymes present in the lysosomes of the liver, pancreas, and kidneys of animals. The purpose of the enzyme is to hydrolyze sulfates in the body. ARSB does this by breaking down Glycosaminoglycans(GAGs), which are large sugar molecules in the body. ARSB targets two GAGs in particular: dermatan sulfate and chondroitin sulfate.

Over 130 mutations to ARSB have been found, each leading to a deficiency in the body. In most cases, the mutation occurs on a single nucleotide in the sequence. An arylsulfatase B deficiency can lead to an accumulation of GAGs in lysosomes, which in turn can lead to Maroteaux–Lamy syndrome, or mucopolysaccharidosis VI.

Structure
The primary structure of Escherichia coli arylsulfatase B contains a primary sequence of 502 amino acids. Its secondary structure is quite complex, containing numerous alpha helices (20 total containing 138 residues) and beta sheets (21 strands total containing 87 residues). The functional enzyme is believed to be a homo tetramer. Due to the complexity of arylsulfatase B's secondary structure, many hydrophobic and hydrophilic regions are present, as demonstrated by the Kyte-Doolittle hydropathy plot:



Additional structural data is shown in Ramachandran analysis plots at: http://www.rcsb.org/pdb/images/3ED4_ram_m_500.pdf.