Lysosomes, human liver

Figure 47-4 Portions of two human liver cells showing the relationship of the organelles and a typical bile canaliculus (BC). Arrowheads indicate light junctions, N, Nucleus M, mitochondria Mb, microbody G, Golgi SER, smooth endoplasmic reticulum L, lysosome g, glycogen. (From Zakim 0, Boyer TD. Hepatology A tejctbook of liver disease, 3rd ed. Philadelphia WB Saunders, 1996 20.)...

P-Galactosidase. Lysosomal P-galactosidase can be purified from human liver or placenta with conventional methods (Meisler, 1972 Sloan, 1972 Miyatake and Suzuki, 1975) or with affinity chromatography on immobilized />-aminophenyl- or 6-aminohexyl-thio-3-D-galactoside (Miller et al., 1977 Lo et al., 1979). The most rapid and convenient procedure seems to be the two-step method of Miller et al. (1977), which is reported to give a more than 20,000-fold purification with 41% yield. The affinity gel is commercially available. 

D-Gluconamide, D-gluconyl hydrazide, and iV-(6-aminohexyl)-D-gluconamide have been tested for their inhibitory action on human liver lysosomal gluco-cerebrosidase and human spleen neutral aryl jS-D-glucosidase (see p. 437). 

Affinity chromatography of acid ribonuclease 268 from He La cell lysosomes demonstration that the enzyme is a glycoprotein Purification of human liver acid a-D- 148... 

All the lysosomal thiol proteinases described in Section II have been isolated only recently and few structural studies have been carried out. The amino acid composition of only cathepsin B has been reported and is quite similar to those of cathepsin B from human liver (75) and rat liver (19) however Ouchterlony double difPiision analysis with antiserum against rat liver cathepsin B showed no immunological cross reactivity (40). All the lysosomal enzymes examined were shown to contain carbohydrate. The 111 of Asn is a glycosylation site in rat liver cathepsin B (128) but no detailed analysis of this carbohydrate has been reported. Since human liver cathepsin H can be purified on Con A-Sepharose (12), it may also contain a carbohydrate moiety. Rat liver cathepsin H and L also bind to Con A-Sepharose. 

Sphingomyelinase is believed to be a lysosomal enzyme. It has been partially purified from human liver and spleen. Isoelectric focussing of a partially purified preparation of the enzyme has permitted iden-... 

Clostridium perfringens Vibrio cholerae Arthrobacter ureafaciens Newcastle disease virus Influenza A2 virus Fowl plague virus Rat liver Golgi Human liver lysosomal Human fibroblast... 

The lysosomes in human liver had more heterogeneous migration characteristics upon fractionation than those in rat liver. A fluffy layer seen in tlie rat fractionation procedure is thus not seen so clearly marked in... 

Sialidase activities in light and heavy lysosomal fractions have been characterized in rat mammary gland (Tulsiani and Carubelli, 1971), human liver (Meyer et al., 1981), and mouse brain (Fiorilli et al., 1991). The heavy lysosomal fraction shows higher specific enzyme activity than the light fraction, but there is no difference in pH optimum, value, or substrate specificity between the two fractions. In mouse brain, the sialidase activities in the heavy and light lysosomal fractions exhibit different developmental profiles, suggesting that the expression of these activities may be regulated independently (Fiorilli et al.y 1991). 

Regarding the effect of Ca + on the activity of lysosomal enzymes, conflicting results have been reported in the literature. Ca + has been reported to have no effect on the activity of the enzyme from rat mammary gland (Tulsiani and Carubelli, 1971), rat liver (Miyagi and Tsuiki, 1984), or rat brain (Miyagi et aL, 1990a), but, at a concentration of 1 mM, slightly stimulates sialidase activity in human leukocytes (Schauer and Wember, 1984) and human liver (Michalski et... 

Most lysosomal sialidases preferentially catalyze the hydrolysis of the a2-3-linked sialic acids compared to the a2-6 residues. Exceptions to this are the enzymes from rabbit spermatozoal acrosomes (Srivastava and Abou-Issa, 1977) and human liver (Michalski et aL, 1982), which are more active on a2-6-linked sialic acids on glycoproteins, i.e., Cowper s gland mucin or submandibular gland mucin. The enzymes from human liver and porcine testis are more active on a2-8-linked sialic acids in colominic acid than other lysosomal enzymes (Table III). 

Michalski, J. C., Corfield, A. P., and Schauer, R., 1986, Properties of human liver lysosomal sialidase, Hoppe-SeylePs Z. Physiol. Chem. 367 715-722. 

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