bio 11.11 - Teus 11.11 Hydrolases are transported via...

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Teus 11.11 Hydrolases are transported via vesicle transport to the lysosome How are the hydrolysis transported to the Ly ????? The transport of hydrolases to the lysosome is well investigated. It dependes on groups of mannose-6-phosphate residues ( M6P ) , - which are transferred on N-linked oligosaccharids during transfer through the Golgi stack. - Receptor proteins (cargo receptors!) recognize the M6P, - which is then dispatched in the TGN “trans Golgi network” in clathrin coated vesicles for the transport to the lysosome. - Due to the low pH the binding of the hydrolase to the M6P- receptor (M6PR) is lost. “so the hydrolyze are released” - The M6PR are transported back in a retrieval pathway using retromer coated vesicles for the next cycle. - The M6P tag is added to the hydrolase within the Golgi. The signal for that is a so called signal patch of amino acids. - M6P is formed after transient transfer of GlcNac-phosphate by GlcNAc-phosphotransferase . The glucose is cleaved leaving the phosphate at the mannose residue. 1 retomer
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Hydrolases receive a mannose-6-phosphate signal for transfer to the lysosome The transfer of GlcNAc by the transferase is strictley controlled . - The GlcNAc-transferase recognizes the signal patch of the hydrolase at the recognition site . - The catalytic site binds to the mannose residues added within the ER. - After transfer or GlcNAc the glucose residue is removed by a differet enzyme leaving the phosphate group at the mannose. Lack of GlcNAc-transferase leads to the lysosomal storage disease ‚I-cell disease‘ Sym ptoms of I-cell disease: Individuals with ML II typically have severe psychomotor retardation . Typically, failure to thrive and developmental delay are obvious by the age of 6 months. The degree of mental retardation is variable but is usually severe and progressive . Individuals with ML II have the coarse facial findings that can be characteristic of some lysosomal storage diseases and include a high forehead , puffy eyelids, flat nasal bridge, macroglossia (large tongue) and coarsening of facial features. Radiologically, they have dysostosis multiplex ( abnormal bone formation in multiple bones of the body ). Skeletal problems are typically severe and include kyphoscoliosis ( curvature of the spine ), vertebral body anomalies 2
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and claw-hand deformities. Individuals with ML II are prone to carpal tunnel syndrome and can experience pain and loss of feeling in their fingertips . Other musculoskeletal problems include hernias and joint contractures and restriction. Cardiovascular symptoms
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This note was uploaded on 05/30/2010 for the course MEDICEN 2100 taught by Professor Saba during the Spring '10 term at Columbia State Community College.

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bio 11.11 - Teus 11.11 Hydrolases are transported via...

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