HEX A

Role in the organism:

The HEX A gene encodes a beta-hexosaminidase enzyme subunit. This enzyme has been found in lysosomes, organelles in which complex molecules are broken down. The main function of this enzyme is to remove the terminal N-acetylhexosamine residues of carbohydrates and other organic molecules with sugar groups (glycoconjugates). One of the major substrates for beta-hexosaminidase is a class of molecules known as GM2 gangliosides. These compounds are a normal component of the cell membrane and are especially present in neurons.

Role in the disorder (state):

Mutations in the HEXA gene cause Tay-Sach's disease, a fatal recessive lysosome disorder in which excess GM2 ganglioside accumulates in neurons. This results in progressive neurodegeneration and death. Tay-Sach's disease is rare but there is a high incidence of Ashkenazi Jews and french Canadians in eastern Quebec (1 in 4500 people).