异质性细胞器

The I-cell defect was soon traced to the deficiency of an enzyme(Nacetyglucosamine phosphotransferas e)required for mannose phosphorylation.
The secreted enzymes lacked the mannose phosphate residue that are present on the corresponding enzymes of cells from normal individuals.
Ganglioside GM2
Trihexoe GM2 and globoside Glucocerebroside
TayTay-Sachs disease: the best –studied lysosomal
storage diseases It results from a deficiency of the enzyme β-Nβhexosaminidase A, an enzyme that degrades the ganglioside GM2 GM2 is a major component of the membranes of brain cells ,and in the absence of the hydrolytic enzyme ,the ganglioside accumulates in the bloated lysosomes of brain cells,causing dysfunction In its severe form ,which strikes during infancy ,the disease is chacterized by progressive mental and motor retardation, as well as skeletal ,cardiac,and resiratory abnormalities
Second Lys
The Functions of Lysosomes
Lysosomes are involved in three major cell functions: ① phagocytosis（吞噬） （吞噬）
A summary of the phagocytic pathway
② autophagy（自吞） （自吞）
③ endocytosis（内吞 （ 作用） 作用）
Disorders Resulting from Defects in lysosomal Function
I-cell disease : Many cells in these patients contain lysosomes that are bloated with undergraded materials. When fibroblasts from these patients were studied in culture ,it was found that lysosomal enzymes are synthesized at normal levels but are secreted into the medium and not targeted to lysosomes.
Electron micrograph of a mitochondrion and peroxisome(过 氧化物酶体)enclosed in a double membrane wrapper derived from the ER.This autophagic vacuole would have fused with a lysosome and its contents digested.
Other lysosomal storage diseases
Disease GM1 GangliosidGangliosidosis TayTay-Sachs diease Fabry’s disease Sandhoff’sdis ease Gaucher’s disease Enzyme Deficiency GM1 ββGalactosidase Hexosaminidas eA αGalactosidase A Hexosaminidas e A and B Glucocerebrosi dase Principle Storage substance Ganglioside GM1 consequences Mental retardation,liver enlargement,skeletal involvement,death by age 2 Mental retardation,blindness,death by age 3 Skin rash,kidney failure,pain in lower extremities Similar to Tay-Sachs diease but Taymore rapidly progressing Liver and spleen enlargement,erosion of long bones,mental retardation in infantile form only
Disorders Resulting from Defects in Lysosomal Function
Characteristics of Lysosomes
Lysosome is a heterogenous organelle（异质 （ 性细胞器） 性细胞器）: Primary lysosome（初级 （ 溶酶体） 溶酶体） Second lysosomes（次 （ 级溶酶体） 级溶酶体） heterophagic 异噬溶酶体） （异噬溶酶体） autophagic 自噬溶酶体） （自噬溶酶体） Residual body 残余小体） （残余小体） Primary Lys
Pompe disease: a fatal inherited condition
in the absence ofα-glucosidase ,undigested glycogen ofαaccumulated in lysosomes,causing swelling of the organelles and irreversible damage to the cells and tissues Diseases of this type, characterized by the deficiency of a single lysosomal enzyme and the corresponding accumulation of undergraded substrate,are called lysosomal storage diseases