Summary

We present evidence that a 480G “)-A transition in the coding region of the P-glucuronidase gene, which results in an aspartic-acid-to-asparagine substitution at amino acid position 152 (D152N), produces a pseudodefi ciency allele (GUSBp) that leads to greatly reduced levels of P-glucuronidase activity without apparent deleterious consequences. The 480G~>A mutation was found ini tially in the pseudodeficient mother of a child with mu copolysaccharidosis VII (MPSVII), bu t it was not on her disease-causing allele, which carried the L176F muta tion. The 480G-+A change was also present in an unre lated individual with another MPSYII allele who had unusually low P~glucuronidase activity, but whose clini cal symptoms were probably unrelated to P-glucuroni dase deficiency. This individual also had an R357X m