Showing papers by "Elina Ikonen published in 1991"

Aspartylglucosaminuria: cDNA encoding human aspartylglucosaminidase and the missense mutation causing the disease.

Abstract: We have isolated a 21 kb cDNA which encodes human aspartylglucosaminidase (AGA, EC 35126) The activity of this lysosomal enzyme is deficient in aspartylglucosaminuria (AGU), a recessively inherited lysosomal accumulation disease resulting in severe mental retardation The polypeptide chain deduced from the AGA cDNA consists of 346 amino acids, has two potential N-glycosylation sites and 11 cysteine residues Transient expression of this cDNA in COS-1 cells resulted in increased expression of immunoprecipitable AGA protein Direct sequencing of amplified AGA cDNA from an AGU patient revealed a G----C transition resulting in the substitution of cysteine 163 with serine This mutation was subsequently found in all the 20 analyzed Finnish AGU patients, in the heterozygous form in all 53 carriers and in none of 67 control individuals, suggesting that it represents the major AGU causing mutation enriched in this isolated population Since the mutation produces a change in the predicted flexibility of the AGA polypeptide chain and removes an intramolecular S-S bridge, it most probably explains the deficient enzyme activity found in cells and tissues of AGU patients

Spectrum of mutations in aspartylglucosaminuria.

Abstract: Aspartylglucosaminuria (AGU) is an inherited lysosomal storage disorder caused by the deficiency of aspartylglucosaminidase We have earlier reported a single missense mutation (Cys163----Ser) to be responsible for 98% of the AGU alleles in the isolated Finnish population, which contains about 90% of the reported AGU patients Here we describe the spectrum of 10 AGU mutations found in unrelated patients of non-Finnish origin Since 11 out of 12 AGU patients were homozygotes, consanguinity has to be a common denominator in most AGU families The mutations were distributed over the entire coding region of the aspartylglucosaminidase cDNA, except in the carboxyl-terminal 17-kDa subunit in which they were clustered within a 46-amino acid region Based on the character of the mutations, most of them are prone to affect the folding and stability and not to directly affect the active site of the aspartylglucosaminidase enzyme

Human leucocyte aspartylglucosaminidase. Evidence for two different subunits in a more complex native structure.

Abstract: Human leucocyte aspartylglucosaminidase (AGA: 1-aspartamido-beta-N-acetylglucosamine amidohydrolase, EC 3.5.1.26) was purified to homogeneity by using affinity chromatography, gel filtration, chromatofocusing and reverse-phase h.p.l.c. As shown by SDS/PAGE, the homogeneous purified enzyme preparation consists of four polypeptide chains with molecular masses of 25, 24, 18 and 17 kDa. In the native polyacrylamide gel these polypeptides migrate as one active enzyme complex, and by gel filtration the peak of enzyme activity can be detected in a position of about 65 kDa. Digestion with endoproteinase Lys-C or endoproteinase Asp-N, followed by peptide analysis with reverse-phase h.p.l.c., reveals an identical peptide pattern for the 24 and 25 kDa bands as well as for the 17 and 18 kDa bands. This treatment further demonstrated a totally different peptide pattern for the 24/25 kDa versus the 17/18 kDa subunit. The N-terminal sequences of the 17 kDa and the 18 kDa peptides were identical, as determined by Edman degradation. The N-termini of the 24 kDa and the 25 kDa peptides were blocked. The enzyme was partly resistant to endoglycosidases H and F, but N-glycosidase F transformed the 24/25 kDa band into one 23 kDa band and the 17/18 kDa band into one 16 kDa band. Also, immunological data obtained with antisera produced against these subunits showed that AGA consists of two non-identical polypeptides.