Читать книгу Cell Biology - Stephen R. Bolsover - Страница 43

Mitochondria are frequently found close to another membrane‐bound organelle, the peroxisome (Figure 1.2 on page 5). In human cells peroxisomes have a diameter of about 500 nm and their dense matrix contains a heterogeneous collection of proteins concerned with a variety of metabolic functions, some of which are only now beginning to be understood. Peroxisomes are so named because they are frequently responsible for the conversion of the highly reactive molecule hydrogen peroxide (H₂O₂), which is formed as a by‐product of the reactions in the mitochondrion, into water. This reaction is carried out by a protein called catalase, which sometimes forms an obvious crystal within the peroxisome. Catalase is an enzyme – a protein catalyst that increases the rate of a chemical reaction. In fact, it was one of the first enzymes to be discovered. In humans, peroxisomes are primarily associated with lipid metabolism. Understanding peroxisome function is important for a number of inherited human diseases such as X‐linked adrenoleukodystrophy where peroxisome malfunction and the consequent inability to metabolize lipid properly typically leads to death in childhood or early adulthood unless dietary lipid is extremely restricted.