A fluorimetric enzyme assay for the diagnosis of Sanfilippo disease C (MPS III C).
Both the alpha- and beta-anomers of 4-methylumbelliferyl-D-glucosaminide were synthesized and shown to be substrates for the lysosomal acetyl-CoA:glucosaminide N-acetyltransferase. Using the beta-anomer, fibroblasts and leukocytes from 11 different Sanfilippo C patients showed < 1% of mean normal N-acetyltransferase activity. Heterozygotes showed intermediate activities. The enzymatic liberation of the fluorochrome from 4-methylumbelliferyl-beta-D-glucosaminide requires the sequential action of the N-acetyltransferase and beta-hexosaminidase. Normal beta-hexosaminidase activity caused complete hydrolysis of the reaction intermediate 4-methylumbelliferyl-beta-D-N-acetylglucosaminide formed by the N-acetyltransferase. In cell extracts with a beta-hexosaminidase deficiency, however, a second incubation in the presence of excess beta-hexosaminidase is needed to avoid underestimation of the N-acetyltransferase activity.
Voznyi YaV
Institute of Biochemistry, Academy of Sciences Armenian Republic, Yerevan.
Karpova
E A
EA
Dudukina
T V
TV
Tsvetkova
I V
IV
Boer
A M
AM
Janse
H C
HC
van Diggelen
O P
OP
D000123:Acetyltransferases / Q000172:deficiency / Q000378:metabolism*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000201:enzymology; D005470:Fluorometry; D006579:Heterozygote; D006801:Humans; D006923:Hymecromone / Q000031:analogs & derivatives / Q000378:metabolism; D007962:Leukocytes / Q000201:enzymology; D009084:Mucopolysaccharidosis III / Q000175:diagnosis* / Q000201:enzymology; D012016:Reference Values
C008511:4-methylumbelliferyl-beta-glucosaminide; D006923:Hymecromone; D000123:Acetyltransferases; C020580:glucosamine acetyltransferase