Substrate. Significance: ARSK functions in lysosomal degradation, possibly of glycosaminoglycans, and, in all probability, is associated with a non-classified lysosomal storage disorder. The human sulfatase household has 17 members, 13 of which happen to be characterized biochemically. These enzymes specifically hydrolyze sulfate esters in glycosaminoglycans, sulfolipids, or steroid sulfates, thereby playing crucial roles in cellular degradation, cell signaling, and hormone regulation. The loss of sulfatase Complement C5/C5a Protein Storage & Stability activity has been linked to extreme pathophysiological conditions for instance lysosomal storage disorders, developmental abnormalities, or cancer. A novel member of this household, arylsulfatase K (ARSK), was identified bioinformatically by way of its conserved sulfatase signature sequence directing posttranslational generation in the catalytic formylglycine residue in sulfatases. However, overall sequence identity of ARSK with other human sulfatases is low (18 ?two ). Here we demonstrate that ARSK indeed shows desulfation activity toward arylsulfate pseudosubstrates. When expressed in human cells, ARSK was detected as a 68-kDa glycoprotein carrying at the least four N-glycans of each the complicated and high-mannose variety. Purified ARSK turned more than p-nitrocatechol and p-nitrophenyl sulfate. This activity was dependent on cysteine 80, which was verified to undergo conversion to formylglycine. Kinetic parameters have been similar to these of many lysosomal sulfatases involved in degradation of sulfated glycosaminoglycans. An acidic pH optimum ( four.6) and colocalization with LAMP1 verified lysosomal functioning of ARSK. Additional, it carries mannose 6-phosphate, indicating lysosomal sorting by way of mannose 6-phosphate receptors. ARSK mRNA expression was located in all tissues tested, suggesting a ubiquitous physiological substrate and a so far non-classified lysosomal storage disorder within the case of ARSK deficiency, as shown ahead of for all other lysosomal sulfatases.Sulfatases represent an evolutionary conserved enzyme household that comprises 17 members in humans (1, two). These enzymes catalyze the hydrolysis of sulfate esters of a number of substrates including glycosaminoglycans (heparin, heparan sulfate, chon- This function was supported by the Deutsche Forschungsgemeinschaft andShire Human Genetic Therapies Inc. (Lexington, MA). Both authors contributed equally to this function. 2 To whom correspondence should be addressed: Dept. of Chemistry, Biochemistry I, Bielefeld University, Universit sstr. 25, 33615 Bielefeld, Germany. Tel.: 49-521-1062092; Fax: 49-521-1066014; E-mail: thomas. [email protected]/dermatan sulfate, and keratan sulfate), sulfolipids (e.g. cerebroside-3-sulfate), and sulfated hormones (e.g. dehydroepiandrosteron-3-sulfate), thereby contributing either to the degradation of CXCL16 Protein Biological Activity macromolecules and cellular elements or hormone activation (three, four). Two sulfatases act on the cell surface as editors in the sulfation status of heparan sulfate proteoglycans (5?) and, thereby, regulate fundamental signaling pathways involving a lot of heparan sulfate-dependent growth things and morphogens (to get a evaluation, see Ref. 8). In humans, sulfatases show functional and structural homologies but show strict specificity toward their natural substrate. Every enzyme catalyzes a precise desulfation step, therefore explaining the non-redundancy of sulfatases in vivo. In vitro, on the other hand, many human sulfatases share activity against tiny sulfated aromatic pseudosubstrates like p-nitroc.
