AGE-DEPENDENT VARIATIONS OF THE HUMAN N-ACETYL-β-D-HEXOSAMINIDASES

The total N-acetyl-β-d -hexosaminidase (hexosaminidase A plus B) activity of the human brain increases during life until the age of 70 years to about twice the activity found in the foetal brain. This activity roughly parallels the increasing level of brain ganglio-sides. Simultaneously, the ratio between the hexosaminidases A and B changes from approx. 3.4 to 1.1 as established by the microscale isoelectric focussing of the enzymes from crude extracts. Age-dependent variations can be also demonstrated for other glycosidase activities: The β-d -glucosidase is shown to increase, the α-d -mannosidase and α-l -fucosidase to decrease during life. The enzyme values are related to the protein content, the age-dependent shift of which we have determined in the human brain. In different organs and body liquids distinct differences are found for the levels of the total hexosaminidase activity as well as for the hexosaminidase pattern. The relation of the hexosaminidase activity to the ganglioside degradation during the human development is discussed.