Title : Crystal structure of a covalent intermediate of endogenous human
arylsulfatase A
Abstract :
- The structures of human arylsulfatase A crystals soaked in solutions containing 4-methylumbelliferyl phosphate and O-phospho-DL- tyrosine have been determined at 2.7- and 3.2-A resolution, respectively
- The formylglycine in position 69, a residue crucial for catalytic activity, was unambiguously identified in both structures as forming a covalent bond to the phosphate moiety
- A hydroxyl group is present at the Cbeta of residue 69 and the formation of one out of two possible stereomeric forms is strongly favoured
- The structures confirm the importance of the gem-diol intermediate in the arylsulfatase's catalytic mechanism
- The presence of an apparently stable covalent bond is consistent with the weak phosphatase activity observed for human arylsulfatase A
- The structures of the complexes suggest that phosphate ions and phosphate esters inhibit arylsulfatase in non-covalent and covalent modes, respectively
- The metal ion present in the active site of arylsulfatase A isolated from human placenta is Ca(2 +) and not Mg(2 +) as was found in the structure of the recombinant enzyme