Beta-ketoacyl-ACP synthase II

Beta-ketoacyl-ACP synthase II (KAS II) is an enzyme crucial in the fatty acid synthesis pathway, specifically involved in the elongation of the carbon chain in fatty acids. This enzyme, along with its counterparts KAS I and KAS III, plays a pivotal role in the biosynthesis of fatty acids in both prokaryotes and eukaryotes, although its function and presence may vary across different organisms.

Function

Beta-ketoacyl-ACP synthase II catalyzes the condensation reaction between malonyl-ACP and an acyl-ACP, which is a longer chain acyl carrier protein (ACP). This reaction extends the acyl chain by two carbons. Unlike KAS I, which is involved in the initial steps of fatty acid elongation, KAS II is responsible for the subsequent elongation steps, making it essential for the production of long-chain fatty acids. The enzyme's activity is crucial for the synthesis of cellular membranes and energy storage molecules, impacting cell structure and energy regulation.

Structure

The structure of KAS II is characterized by a thiolase fold, consisting of an α/β/α sandwich configuration. This configuration allows for the binding of acyl carrier protein substrates and the catalytic activity necessary for chain elongation. The active site of KAS II contains a cysteine residue that acts as a nucleophile in the condensation reaction. The enzyme's structure is highly conserved across different species, reflecting its essential role in fatty acid synthesis.

Biological Importance

In plants, KAS II is particularly important in the synthesis of unsaturated fatty acids, which are crucial components of chloroplast membranes and play a role in plant temperature adaptation. In bacteria, the enzyme is involved in the synthesis of membrane lipids, affecting bacterial membrane fluidity and, consequently, the ability of bacteria to survive under different environmental conditions.

Inhibition and Antibacterial Targets

Given its essential role in fatty acid synthesis, KAS II is a target for antibacterial compounds. Inhibitors of KAS II can disrupt fatty acid synthesis in bacteria, leading to cell death. This makes KAS II a potential target for the development of new antibacterial drugs, especially in the face of increasing antibiotic resistance.

Genetic Regulation

The expression of the KAS II gene is tightly regulated, ensuring that fatty acid synthesis occurs in response to cellular needs. In bacteria, the regulation of KAS II involves complex genetic networks that respond to environmental signals and nutritional status, allowing the bacteria to adapt its membrane composition accordingly.

Clinical Relevance

Research into KAS II has implications for understanding metabolic diseases in humans, such as obesity and diabetes, where fatty acid metabolism is disrupted. Additionally, the enzyme's role in bacterial fatty acid synthesis makes it a potential target for novel antibacterial therapies.

See Also

• Fatty acid synthesis
• Acyl carrier protein
• Enzyme
• Metabolism
• Antibacterial