Zsírsavszintáz

Zsírsavszintáz, often abbreviated as FAS, is a multi-enzyme complex crucial for fatty acid synthesis in living organisms. It is a large protein found in the cytoplasm of cells in eukaryotes and in the cytosol of bacteria and archaea. The primary function of zsírsavszintáz is to catalyze the formation of long-chain saturated fatty acids from acetyl-CoA and malonyl-CoA precursors. This process is an anabolic pathway, meaning it builds up larger molecules from smaller ones, requiring energy in the form of ATP and reducing power from NADPH.

The zsírsavszintáz enzyme complex in mammals is a homodimer, meaning it consists of two identical polypeptide chains, each containing all the catalytic activities necessary for fatty acid synthesis. These activities include condensation, reduction, and dehydration steps, all integrated into a single molecular machinery. The reaction begins with the loading of an acetyl group and a malonyl group onto the enzyme's acyl carrier protein (ACP) domain. Subsequent reactions involve the sequential addition of two-carbon units from malonyl-CoA to the growing fatty acid chain, with reduction steps utilizing NADPH to convert ketoacyl intermediates into hydroxylacyl intermediates, and finally into saturated acyl chains. The most common product synthesized by zsírsavszintáz is palmitate, a 16-carbon saturated fatty acid.

Regulation of zsírsavszintáz activity is tightly controlled to meet the cell's metabolic needs. Hormones like insulin promote its synthesis and activity, reflecting the body's energy storage state. Conversely, fasting and glucagon inhibit its production. Genetic defects or dysregulation of zsírsavszintáz can lead to various metabolic disorders. Its significant role in lipogenesis makes it a target for research in areas such as obesity, diabetes, and cancer, where aberrant fatty acid metabolism is implicated.