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Hexosaminidase-A and Hexosamini-dase-B: Studies in Tay-Sachs' and Sandhoff's Disease


HUMAN tissues contain two isozymes of β-D-N-acetyl-hexos-aminidase1. Hexosaminidase-A (hex-A) is thermolabile and moves toward the anode on electrophoresis at pH 6.0, and hexosaminidase-B (hex-B) is relatively thermostable and moves toward the cathode. In Tay-Sachs' disease, which is found predominantly in Jewish populations, hex-A is absent but hex-B activity is increased2–5. In Sandhoff's disease, a variant of Tay-Sachs' disease, found mostly in non-Jewish populations, both enzyme activities are missing3,6. Thus, while it is apparent that there is a genetic relationship between hex-A and hex-B, the nature of this relationship has remained obscure. It has been suggested that hex-A may be derived from hex-B by the addition of neuraminic acid residues1,7.

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