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Hydrolases in lysosomes

The degradation of proteins by acid hydrolases in lysosomes involves vesicle fusion through three main pathwaysautophagy, endocytosis, and phagocytosis. The low pH inside lysosomes is maintained by an ATP driven proton pump. [Pg.775]

The anatomic sites (subcellularly) and the details of the enzymatic processes involved in the hydrolysis of chylomicron cholesteryl esters newly taken up by the liver have not been fully defined. It is clear that one of the major processes consists of receptor-mediated endocytosis of chylomicron remnants, followed by hydrolysis of cholesteryl esters and other remnant components within lysosomes. In rare genetic diseases characterized by lysosomal acid lipase deficiency (Wol-man s disease and cholesteryl ester storage disease), cholesteryl esters accumulate in liver cells and in other tissues as well [see Assmann and Frederickson (1983) for review and references]. An acid cholesteryl ester hydrolase from rat liver lysosomes has been partially purified and characterized (Brown and Sgoutas, 1980 Van Berkel etal., 1980). Enzymatic activity was found in preparations of both parenchymal and nonparenchymal liver cells (Van Berkel et al., 1980). Hydrolysis of chylomicron cholesteryl esters taken up by isolated rat hepatocytes was inhibited by chloroquine (Florin and Nilsson, 1977), an agent which inhibits the action of acid hydrolases in lysosomes. Finally, there is also evidence that the rate of cholesteryl ester hydrolysis may be limited by the rate at which internalized remnant particles are moved to the presumably lysosomal site of hydrolysis (Nilsson, 1977 Florin and Nilsson, 1977 Cooper and Yu, 1978). [Pg.20]

Early endosomes are the main sorting station in the endocytic pathway. In their acidic interior (pH 5.9-6.0), the receptor and its ligand can be released. The receptor may be recycled to the surface by vesicles that fuse with the plasma membrane. Material that cannot escape from the early endosomes is further transported via multivesicular bodies to late endosomes and digesting lysosomes that contain a broad spectrum of peptidases and hydrolases in an acidic surrounding [for reviews on endocytosis see Refs. (10-12), for review on clathrin uptake see Refs. (9,13)]. [Pg.343]

In contradistinction to the decrease in lysosomal enzyme activity observed in alveolar macrophages and bronchial lavage fluid, Dillard et al. reported that continuous ozone exposure (0.70-0.79 ppm for 5-7 days) resulted in an increase in the activity of some lysosomal hydrolases in rat whole-lung homogenates and lung fractions, including the soluble supernatant. The tocopherol concentrations of the diet had no effect on the findings. [Pg.357]

Continuous for 5-7 days Increased activity of lysosomal hydrolases in whole-lung homogenates Rat 48... [Pg.372]

Glycosaminoglycans are degraded in lysosomes, which contain hydrolytic enzymes that are most active at a pH of approximately 5. [Note Therefore, as a group, these enzymes are called acid hydrolases.] The low pH optimum is a protective mechanism that prevents the enzymes from destroying the cell should leakage occur into the cytosol where the pH is neutral. With the exception of keratan sui-... [Pg.160]

Since lysosomes are involved in digesting a whole range of biological material, exemplified by the destruction of a whole bacterium with all its different types of macromolecules, it is not surprising to find that a large number of different hydrolases reside in lysosomes. These enzymes catalyze the breakdown of nucleic acids, proteins, cell wall carbohydrates, and phospholipid membranes (see Table 1.1). [Pg.9]

Other glycoenzymes of the hydrolase type listed in Table I include mammalian,43 yeast,44 and plant5,9,49-51 proteases, and mammalian esterases53 and phosphatases.53 Several of the lysosomal hydrolases in... [Pg.308]

Defect in lysosomal cholesteryl ester hydrolase affects metabolism of LDLs... [Pg.104]

Ml. Maggi, V., Lysosomal and non-lysosomal localization of acid hydrolases in animal cells. Biochem. J. Ill, 25P-26P (1969). [Pg.143]

D-Amino acid oxidase occurs in peroxisomes containing other enzymes that produce H2O2 (e.g., L-a-hydroxy acid oxidase, citrate dehydrogenase, and L-amino acid oxidase) and catalase and peroxidase, which destroy H2O2. In leukocytes, killing of bacteria involves hydrolases of lysosomes and production of H2O2 by NADPH oxidase (Chapter 15). Conversion of D-amino acids to the corresponding a-keto acids removes the asymmetry at the a-carbon atom. The keto acids may be aminated to L-amino acids. By this conversion from D- to L-amino acids, the body utilizes D-amino acids derived from the diet ... [Pg.336]

Vitamin A is a surfactant, and its toxicity may be due to labilization and disruption of biological membranes. Excessive amounts of retinol also increase synthesis and release of lysosomal hydrolases. In in vitro systems, retinol bound to RBP is not toxic, and RBP alone protects against... [Pg.908]

Inui, K., and Wenger, D. A., Concentrations of sphingolipid hydrolases in liver and brain samples from patients with lysosomal storage diseases. J. Clin. Invest. 72, 1622-1628. (1983). [Pg.194]

Peltonen, L., Puranen, J., and Korhonen, S., Lysosomal hydrolases in different compartments of rheumatoid and osteoarthrotic joints. Scand. J. Rheumatol. 10, 97-106 (1981). [Pg.198]

Lindmark, D. J. (1988) Giardia lamblia localization of hydrolase activities in lysosome-like organelles of trophozoites. Exp. Parasitol. 65 141 147. [Pg.252]


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See also in sourсe #XX -- [ Pg.327 ]




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In lysosomes

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Lysosomes

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