Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
$\beta$-ketoacyl ACP synthase is a critical enzyme involved in the biosynthesis of fatty acids. It catalyzes the addition of a two-carbon unit to the growing fatty acid chain, a key step in the iterative process of fatty acid elongation.
5 Must Know Facts For Your Next Test
$\beta$-ketoacyl ACP synthase is also known as fatty acid synthase (FAS) or 3-ketoacyl-ACP synthase.
It catalyzes the condensation reaction between malonyl-ACP and the growing acyl-ACP chain, adding a two-carbon unit to the chain.
This enzyme is part of the fatty acid synthase complex, which is responsible for the de novo synthesis of palmitic acid (16:0) from acetyl-CoA and malonyl-CoA.
The $\beta$-ketoacyl ACP synthase reaction is repeated iteratively to elongate the fatty acid chain by two carbons with each cycle.
Regulation of $\beta$-ketoacyl ACP synthase activity is crucial for controlling the rate of fatty acid biosynthesis and maintaining cellular lipid homeostasis.
Review Questions
Describe the role of $\beta$-ketoacyl ACP synthase in the biosynthesis of fatty acids.
$\beta$-ketoacyl ACP synthase is a key enzyme in the fatty acid biosynthesis pathway. It catalyzes the condensation reaction between malonyl-ACP and the growing acyl-ACP chain, adding a two-carbon unit to the chain. This iterative process is repeated to elongate the fatty acid to the desired length, typically resulting in the synthesis of palmitic acid (16:0). The regulation of $\beta$-ketoacyl ACP synthase activity is crucial for controlling the rate of fatty acid biosynthesis and maintaining cellular lipid homeostasis.
Explain how $\beta$-ketoacyl ACP synthase is integrated into the overall fatty acid biosynthesis pathway.
$\beta$-ketoacyl ACP synthase is a central component of the fatty acid synthase complex, which is responsible for the de novo synthesis of palmitic acid from acetyl-CoA and malonyl-CoA. The $\beta$-ketoacyl ACP synthase reaction, which adds a two-carbon unit to the growing fatty acid chain, is repeated iteratively to elongate the chain. This enzyme works in coordination with other enzymes, such as acetyl-CoA carboxylase and acyl carrier protein (ACP), to facilitate the step-by-step construction of fatty acids. The regulation of $\beta$-ketoacyl ACP synthase activity is crucial for controlling the overall rate and product distribution of the fatty acid biosynthesis pathway.
Analyze the significance of $\beta$-ketoacyl ACP synthase in the context of cellular lipid metabolism and homeostasis.
$\beta$-ketoacyl ACP synthase plays a pivotal role in cellular lipid metabolism and homeostasis. As the key enzyme responsible for the iterative elongation of fatty acid chains, $\beta$-ketoacyl ACP synthase activity directly determines the availability of fatty acids for the synthesis of various lipid molecules, such as phospholipids, triglycerides, and lipid-based signaling molecules. The regulation of $\beta$-ketoacyl ACP synthase, influenced by factors like nutrient availability and hormonal signals, allows the cell to fine-tune its fatty acid biosynthesis and maintain the appropriate balance of lipids required for membrane structure, energy storage, and signaling functions. Dysregulation of $\beta$-ketoacyl ACP synthase can lead to imbalances in cellular lipid homeostasis, contributing to various metabolic disorders and disease states.
The metabolic pathway responsible for the synthesis of fatty acids, which are essential components of cell membranes and energy storage molecules.
Acetyl-CoA Carboxylase: The enzyme that catalyzes the first committed step in fatty acid biosynthesis, converting acetyl-CoA to malonyl-CoA, the two-carbon building block for fatty acid elongation.
Acyl Carrier Protein (ACP): A small, acidic protein that carries the growing fatty acid chain and shuttles it between the various enzymes involved in fatty acid biosynthesis.