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Inborn Metabolic Diseases Diagnosis and Treatment - part 10

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Peroxisome là bào quan tế bào lấy được tên của họ từ sự hiện diện của catalase, một enzyme có thể chuyển đổi hydrogen peroxide thành oxy và nước. Với các thể tiêu bào, họ được tìm thấy trong tất cả các tế bào của con người ngoại trừ hồng cầu, tuy nhiên, không giống như các thể tiêu bào | 510 Chapter 40 Peroxisomal Disorders Peroxisomal Functions Peroxisomes are cell organelles which derive their name from the presence of catalase an enzyme that converts hydrogen peroxide into oxygen and water. As with lysosomes they are found in all human cells except erythrocytes however unlike lysosomes they possess anabolic besides catabolic functions o Fig. 40.1 . Peroxisomes are mainly involved in lipid metabolism they synthesize ether-phospholipids called plasmalogens which are important constituents of cell membranes and myelin and P-oxidize very long chain fatty acids. Peroxisomes are also involved in the oxidation of phytanic acid a chlorophyll derivative and in the formation of bile acids from mevalonate via cholesterol. In addition they are concerned with the catabolism of lysine via pipecolic acid and glutaric acid o Fig. 23.1 and of glyoxylate o Fig. 43.1 . Phytanic acid Synthetase Phytanoyl-CoA Mevalonate hPhytanoyl-CoA I Mevalonate hydroxylase I kinase 2-OH-phytanoyl-CoA h2-OH-phytanoyl-CoA lyase Pristanal Cholesterol hPristanal dehydrogenase VLCFA Pristanic acid THCA Pristanoyl-CoA Acyl-CoA VLCFA-CoA Acyl-CoA oxidase I Acyl-CoA oxidase II THCA-CoA L Acyl-CoA oxidase II Acyl-DHAP Alkyl-DHAP synthase Alkyl-DHAP D-bifunctional protein D-bifunctional protein Alkyl-G3P Thiolases 1 and 2 Thiolase 2 Etherphospholipids Plasmalogens LC acyl-CoA Acetyl-CoA Trimethyl-tridecanoyl-CoA Propionyl-CoA D-bifunctional protein Cholic acid o Fig. 40.1. Schematic representation of the main peroxisomal functions. CoA coenzyme A DHAP dihydroxyacetone phosphate DHAPAT dihydroxyacetone phosphate acyltransferase G3P glycerol-3-phosphate LC long-chain THCA trihydroxycho-lestanoic acid VLCFA very-long-chain fatty acid 511 40 40.1 Clinical Presentation Peroxisomal disorders can be recognized by the presence of dysmorphic features neurological abnormalities and hepatic and gastrointestinal dysfunction. Widely different features that can occur include the following 4 Craniofacial