Mucopolysaccharidosis II, also known as Hunter Syndrome, is a lysosomal
storage disorder characterized by a deficiency in iduronate-2-sulfatase, an
enzyme responsible for the hydrolysis of the terminal 2-sulfate esters from the
glycosaminoglycans dermatan sulfate and heparin sulfate in the lysosomes of
various cells. This enzyme deficiency causes an accumulation of glycosaminoglycans
(GAGs) in tissue. The clinical manifestations of this deficiency are short
stature, joint stiffness, harsh facial features, hepatosplenomegaly, and progressive
mental retardation. As with other lysosomal storage disorders, the patient’s only
recourse is enzyme replacement therapy (ERT). Idursulfase is a recombinant
human enzyme that has been developed and launched as the ERT for Hunter
syndrome. Unlike most recombinant enzymes, it cannot be produced in prokaryotic
cells. For proper post-translational attachment of N-linked oligosaccharides
and the crucial mannose-6-phosphate groups as the targeting passport into
lysosomes, idursulfase is produced from HT-1080 cells. In addition to being fully
glycosylated with eight mannose-6-phosphate groups, the enzyme possesses
sialylated moieties that improve its stability in circulation.
