Galactosialidosis: a direct evidence that a 46-kilodalton protein restores deficient enzyme activities in fibroblasts.
The intracellular function of a specific protein to protect lysosomal beta-galactosidase and neuraminidase activities against proteases in human fibroblasts was studied. Beta-Galactosidase was purified from human placenta to different degrees; a preparation (A) contained also two concomitant proteins, and a highly purified preparation (B) contained only the mature beta-galactosidase. The protein concentrate of the culture medium of normal fibroblasts restored the activities of the deficient enzymes, beta-galactosidase and neuraminidase, in galactosialidosis cells. This effect was inhibited only by the anti-A anti-serum, and not by the anti-B antiserum. A 46-kilodalton protein, secreted from fibroblasts cultured in the presence of ammonium chloride, was detected again only by the anti-A antiserum, and not by the anti-B antiserum. It was concluded that this protein has a function to restore their activities in fibroblasts from galactosialidosis patients after being endocytosed from the culture medium.
D002478:Cells, Cultured; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D005696:Galactosidases / Q000172:deficiency*; D006801:Humans; D008661:Metabolism, Inborn Errors / Q000378:metabolism*; D008970:Molecular Weight; D009439:Neuraminidase / Q000172:deficiency*; D011506:Proteins / Q000378:metabolism*; D001616:beta-Galactosidase / Q000172:deficiency*
D011506:Proteins; D005696:Galactosidases; D009439:Neuraminidase; D001616:beta-Galactosidase