Abstract
Defined, human genetic diseases due to the absence or malfunction of cytoplasmic enzymes can be divided into two main clusters. In the first, absence of appropriate hydrolytic enzyme activity ordinarily found within the vacuolar apparatus leads to the accumulation of uncleaved substrate in the lysosomes of affected tissue. Such diseases include Tay-Sachs disease, Gaucher’s disease, peroxidase deficiency, and various mucopolysaccharidoses. Among the second group, in which enzyme activity is missing not from the lysosomes, but from non-membrane-bounded portions of the cytosol, are adenosine deaminase deficiency and the Lesch-Nyhan syndrome. Since lysosomal storage diseases are caused by a genetic deficiency of specific acid hydrolases in lysosomes, reversal of such enzyme deficiencies has been approached by means of direct enzyme replacement.
Highlights
Since lysosomal storage diseases are caused by a genetic deficiency of specific acid hydrolases in lysosomes, reversal of such enzyme deficiencies has been approached by means of direct enzyme replacement
Evidenceof increments in theentrapment within anionic liposomeosf horseradish peroxidase (PI 7.2) and hexosaminidase A (PI 5.4), both of which are slightly anionic at pH 7.4(swelling solution), and of the cationic enzyme lysozyme (PI 11.0)withincationic liposomes strongly suggests that these enzymes are free in the aqueouscompartments; they are probably not entrapped as the result ofnonspecific, electrostatic interactions [12, 14, 15]
Small sonicated liposomes are recovered in the plasma at approximately 5-fold higher levels than unsonicated liposomes following intraperitoneal injection and at approximately 10-fold higher levels following intramuscular injection [39]. These results suggest that large liposomes are limited in their ability to penetrate vascular membranes and to pass through small capillaries
Summary
Absence of appropriate hydrolytic enzyme activity ordinarily found within the vacuolar apparatus leads to the accumulation of uncleaved substrate in the lysosomes of affected tissue. Such diseases include Tay-Sachs disease, Gaucher’s disease, peroxidase deficiency, and various mucopolysaccharidoses. Since lysosomal storage diseases are caused by a genetic deficiency of specific acid hydrolases in lysosomes, reversal of such enzyme deficiencies has been approached by means of direct enzyme replacement Because it is the affected system, the lysosomal apparatus of cells, that normally takes u p extracellular macromolecules and particles by endocytosis, attempts have been made to mobilize the stored GM,-ganglioside present in Tay-Sachs disease by direct administration of purified enzyme [1].
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