FabK

FabK is a gene encoding a flavoprotein enoyl-ACP reductase that participates in the fatty acid biosynthesis II pathway found in certain bacteria. The enzyme catalyzes the reduction of enoyl-ACP intermediates to saturated acyl-ACPs, a key step in the iterative elongation of fatty acid chains. Unlike the more common FabI enoyl-ACP reductase used by many bacteria, FabK is a distinct enzyme family with a different cofactor dependence and catalytic properties that enable alternate flux through fatty acid synthesis when FabI activity is limited.

Clinical and research relevance: The FabK enzyme is notable for its insensitivity to triclosan, an antimicrobial compound that inhibits FabI. This difference has made FabK a focus of research into triclosan resistance and the development of inhibitors that target FabK specifically. FabK homologs have been identified in several Gram-positive bacteria, including Streptococcus pneumoniae, and are studied for their roles in physiology and antibiotic response. Structural studies have characterized FabK as a flavoprotein with a distinct active site compared to FabI, informing drug design.

In summary, FabK represents a separate enoyl-ACP reductase in some bacteria, contributing to fatty acid synthesis and offering a target for antibiotics with activity against FabK-containing pathogens.