Tay-Sachs disease: one-step assay of beta-N-acetylhexosaminidase in serum with a sulphated chromogenic substrate |
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Authors: | W Fuchs R Navon M M Kaback H Kresse |
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Institution: | 1. Institute of Physiological Chemistry, University of Münster, D-4400 MünsterFRG;2. Department of Human Genetics, The Chaim Sheba Medical Center, Tel-Hashomer 52621 Israel;3. Division of Medical Genetics, E-4, Harbor General Hospital, Torrance, CA, 90502 USA |
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Abstract: | A sulphated chromogenic compound, p-nitrophenyl-6-sulpho-2-acetamido-2-deoxy-beta-D-glucopyranoside, which can be hydrolysed enzymatically to p-nitrophenol and the sulphated amino sugar, was used as a substrate for the determination of activity of beta-N-acetylhexosaminidase isoenzymes in human serum. The sera of six Tay-Sachs patients lacking isoenzyme A and heat-inactivated control serum exhibited 6% of the mean normal enzyme activity of 1.32 U/l (1-s range = 1.07-1.57 U/l). In 10 obligate carriers of the Tay-Sachs gene the enzyme activity was 52% (1-s range = 45-60%) of the mean normal value. Therefore, by using the sulphated chromogenic substrate Tay-Sachs disease can be diagnosed enzymatically in a simple one-step procedure, but the 2-s activity ranges of heterozygotes and normals overlap. The assay is not absolutely specific for isoenzyme A of beta-N-acetylhexosaminidase, because the substrate can be hydrolysed to a certain extent by beta-N-acetylhexosaminidase I. |
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