Pre-lysosomes

The more acidic late endosomes (pH ca. 5.5 or less) are sometimes referred to as pre-lysosomes. Digestion of the food material or other macromolecules... 

Cathepsin K (Cat K) is a member of the CA1 family of lysosomal cysteine proteases. This family is comprised of 11 human members (cathepsins B, C, F, H, K, L, O, S, V, W, Z) which share a common papain-like structural fold and a conserved active site Cys-Asn-His triad of residues [1-3]. These enzymes are synthesized as pre-pro-enzymes and are converted from the catalytically inactive zymogen into the active form in acidic lysosomal environment. In some cases, cathepsins are also secreted in the active form from cells. The sequence identity of... 

There is also intriguing evidence that (co-3) fatty acids induce apo B degradation via mechanisms that do not involve the conventional proteasomal or lysosomal degradation pathways. In the presence of (cu-3) fatty acids, apo B degradation was shown to occur in a post-ER, pre-secretion process (E.A. Fisher, 2004). Lipid peroxidation and oxidative stress mechanisms were implicated in the increased degradation and decreased secretion of apo... 

The lysosomal mannosidase has been purified from a munber of species [130, 156-160] and the subunit molecular weights vary significantly between species. The human enzyme can be separated into two forms by ion exchange chromatography, termed A and B, but significant evidence indicates that the two enzymes are differently modified versions of the same gene product [156]. Pulse-chase studies have indicated that the initial translation product of the human gene is a 110 kDa pre-... 

Cells take up MT firom the circulation through a megalin/cubilin scavenger receptor pathway [26,27]. The internalized MT then releases cadmium in an endosomal/lysosomal compartment and divalent metal transporter 1 (DMTl) transports cadmium into the cytosol where it binds to extant MT and/or induces additional MT through the release of zinc from extant MT [28]. MT also is secreted from cells [29]. However, the pathway and mechanism of MT secretion remains elusive as in animals and man no pre-protein with an amino acid signature for export has been identified. Cd-MT may cross the plasma membrane of liver and other cells by fluid-phase exocytosis [30]. Extracellular MT is found under a variety of conditions including increasing cadmium loads [31]. 

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