Isoenzimas

Isoenzimas, also known as isozymes, are different molecular forms of the same enzyme that catalyze the same biochemical reaction. These variations arise from differences in their amino acid sequences, which can be due to distinct genes encoding the enzyme or alternative splicing of a single gene. Despite catalyzing the same reaction, isoenzymes can exhibit differences in their kinetic properties, such as their affinity for the substrate (Km) or their maximum reaction velocity (Vmax). They may also differ in their optimal pH or temperature, or in their response to activators or inhibitors. These functional differences allow cells to fine-tune metabolic pathways and respond to varying physiological conditions. Isoenzymes are particularly common in vertebrates and are often tissue-specific. For example, lactate dehydrogenase (LDH) exists as five different isoenzymes, with different distributions in tissues like heart and skeletal muscle. The measurement of specific isoenzymes in biological fluids, such as blood, can be a valuable diagnostic tool for identifying tissue damage. For instance, elevated levels of certain LDH isoenzymes can indicate a heart attack or liver disease.