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The turnover of lysosomal beta-galactosidase was studied in fibroblast cultures from patients with Gm1-gangliosidosis and combined beta-galactosidase and neuraminidase deficiency, which had 5-10% residual beta-galactosidase activity. beta-Galactosidase was specifically inactivated with the suicide substrate beta-D-galactopyranosylmethyl-p-nitro-phenyltriazene (beta-Gal-MNT) and from the subsequent restoration of enzyme activity in cell cultures turnover times were calculated. By using [3H]beta-Gal-MNT, the hydrolytic activity per molecule of beta-galactosidase was determined. 3H-labelled beta-D-galactopyranosylmethylamine, the precursor of [3H]beta-gal-MNT, was obtained by Raney-nickel-catalysed exchange with 3H2O. The rate of synthesis of beta-galactosidase in normal and all mutant cells tested was found to be 0.4-0.5 pmol/day per mg of cellular protein. The GM1-gangliosidosis cells tested contain the normal amount of 0.5 pmol of beta-galactosidase/mg of protein with a normal turnover time of about 10 days, but only 10% of beta-galactosidase activity per enzyme molecule. Cells with combined beta-galactosidase and neuraminidase deficiency contain only 0.3 pmol of beta-galactosidase/mg of protein with a decreased turnover time of 1 day and normal hydrolytic properties (200 nmol of 4-methylumbelliferyl galactoside/h pmol of beta-galactosidase).
O P Van Diggelen, and
A W Schram, and
M L Sinnott, and
P J Smith, and
D Robinson, and
H Galjaard
January 1979,
Biochimica et biophysica acta,
O P Van Diggelen, and
A W Schram, and
M L Sinnott, and
P J Smith, and
D Robinson, and
H Galjaard
April 1978,
Experimental cell research,
O P Van Diggelen, and
A W Schram, and
M L Sinnott, and
P J Smith, and
D Robinson, and
H Galjaard
April 1987,
Clinica chimica acta; international journal of clinical chemistry,
O P Van Diggelen, and
A W Schram, and
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P J Smith, and
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H Galjaard
May 1986,
Human genetics,
O P Van Diggelen, and
A W Schram, and
M L Sinnott, and
P J Smith, and
D Robinson, and
H Galjaard
November 1981,
Biochemical and biophysical research communications,
O P Van Diggelen, and
A W Schram, and
M L Sinnott, and
P J Smith, and
D Robinson, and
H Galjaard
May 1980,
European journal of pediatrics,
O P Van Diggelen, and
A W Schram, and
M L Sinnott, and
P J Smith, and
D Robinson, and
H Galjaard
January 1982,
Journal of inherited metabolic disease,
O P Van Diggelen, and
A W Schram, and
M L Sinnott, and
P J Smith, and
D Robinson, and
H Galjaard
November 1989,
Somatic cell and molecular genetics,
O P Van Diggelen, and
A W Schram, and
M L Sinnott, and
P J Smith, and
D Robinson, and
H Galjaard
May 1978,
Nihon rinsho. Japanese journal of clinical medicine,
O P Van Diggelen, and
A W Schram, and
M L Sinnott, and
P J Smith, and
D Robinson, and
H Galjaard
January 1986,
Biochimica et biophysica acta,
