Hydrolysis of Tay-Sachs ganglioside by beta-hexosaminidase A of human liver and urine.

A crude /I-hexosaminidase fraction prepared by (NH,),SO( fractionation of human liver extract or urine was found to convert Tay-Sachs ganglioside, GalNAcPl -+ 4(NANcrZ -+ 3)Gal/31 --f 4Glc + ceramide (G& into NAN& + 3Galfil -+ 4 Glc + ceramide (GMM3). After separation of hexosaminidase A and B by DEAE-cellulose chromatography, only freshly prepared fi-hexosaminidase A hydrolyzed GM2 although both forms were still active toward P-nitrophenyl-flD-N-acetylglucosaminide. A heat-stable, nondialyzable preparation obtained from the crude /?-hexosaminidase fraction of human liver was found to stimulate the hydrolysis of GM2 by /3-hexosaminidase A but not B isolated from both sources. Upon aging, P-hexosaminidase A would only hydrolyze GRIZ in the presence of the heat-stable preparation. Extensive purification as well as aging tended to reduce the capacity of /?-hexosaminidase A to hydrolyze GM2 even in the presence of the heat-stable preparation. Our results explain why P-hexosaminidase A has been previously reported by other investigators to hydrolyze Glvrz only with great difficulty. Our results also relate the inordinate storage of GRIZ to the absence of P-hexosaminidase A in the classical form of Tay-Sachs disease.