   2.3.1.78 | proteolytic modification |
enzyme is synthesized as a catalytically inactive 77-kDa precursor that is transported to the lysosomes via an adaptor protein-mediated pathway that involves conserved tyrosine- and dileucine-based lysosomal targeting signals in its C-terminal cytoplasmic domain with a contribution from a dileucine-based signal in the N-terminal cytoplasmic loop. In the lysosome, the precursor is cleaved into a 29-kDa N-terminal alpha-chain and a 48-kDa C-terminal beta-chain, and assembled into active 440-kDa oligomers. The subunits are held together by disulfide bonds between at least two cysteine residues, Cys123 and Cys434, in the lysosomal luminal loops of the enzyme. Proteolytic cleavage may allow the nucleophile residue, His269, in the active site to access the substrate acetyl-CoA in the cytoplasm, for further transfer of the acetyl group to the terminal glucosamine on heparan sulfate |
719889 |
