Question

What is the difference between the type of oxidation catalyzed by acyl-CoA dehydrogenase and that catalyzed by \(\beta\) -hydroxyCoA dehydrogenase?

Short answer

Acyl-CoA dehydrogenase uses FAD to oxidize acyl-CoA; \(\beta\)-hydroxyCoA dehydrogenase uses NAD\textsuperscript{+} to oxidize \(\beta\)-hydroxyacyl-CoA.

Step-by-step solution

- Understand the Enzymes

Identify and understand the function of the two enzymes involved: acyl-CoA dehydrogenase and \(\beta\)-hydroxyCoA dehydrogenase.

- Look at Acyl-CoA Dehydrogenase Function

Acyl-CoA dehydrogenase catalyzes the first step in the \(\beta\)-oxidation pathway of fatty acid metabolism. It catalyzes the oxidation of acyl-CoA, introducing a double bond to create a trans-enoyl-CoA and reduces FAD to FADH\textsubscript{2}.

- Look at \(\beta\)-hydroxyCoA Dehydrogenase Function

\(\beta\)-hydroxyCoA dehydrogenase catalyzes a later step in the \(\beta\)-oxidation pathway. It catalyzes the oxidation of \(\beta\)-hydroxyacyl-CoA to \(\beta\)-ketoacyl-CoA and reduces NAD\textsuperscript{+} to NADH.

- Compare the Electron Acceptors

Identify the difference in electron acceptors: Acyl-CoA dehydrogenase uses FAD, while \(\beta\)-hydroxyCoA dehydrogenase uses NAD\textsuperscript{+}.

- Define the Key Difference

The key difference lies in the oxidation of different types of molecules and their respective electron acceptors.

Key concepts

acyl-CoA dehydrogenase

Acyl-CoA dehydrogenase is an enzyme that plays a crucial role in the β-oxidation of fatty acids. This enzyme catalyzes the first step in the pathway by oxidizing acyl-CoA. The process introduces a double bond into the fatty acid chain, converting it into a trans-enoyl-CoA. During this reaction, the electron acceptor flavin adenine dinucleotide (FAD) is reduced to FADH₂. This conversion is essential for the continuation of the β-oxidation cycle, leading to the eventual production of energy in the form of ATP.

In simple terms:

• Acyl-CoA dehydrogenase initiates the breakdown of fatty acids.
• It introduces a double bond into the acyl-CoA.
• FAD is the electron acceptor, becoming FADH₂ in the process.

beta-hydroxyCoA dehydrogenase

β-HydroxyCoA dehydrogenase is another enzyme involved in the β-oxidation pathway but operates later than acyl-CoA dehydrogenase. This enzyme catalyzes the oxidation of β-hydroxyacyl-CoA to β-ketoacyl-CoA. The primary distinction here is that the electron acceptor in this reaction is nicotinamide adenine dinucleotide (NAD⁺). NAD⁺ gets reduced to NADH during the reaction. This step is crucial for the continuation of fatty acid metabolism, transforming the substrate into a form that can be further processed for energy production.

In simpler terms:

• β-HydroxyCoA dehydrogenase acts later in the β-oxidation cycle.
• It converts β-hydroxyacyl-CoA into β-ketoacyl-CoA.
• NAD⁺ is the electron acceptor, becoming NADH.

fatty acid metabolism

Fatty acid metabolism is a series of biochemical processes breaking down fatty acids to produce energy. The primary pathway involved is β-oxidation, which occurs in the mitochondria. The metabolism involves several steps where each step is catalyzed by specific enzymes like acyl-CoA dehydrogenase and β-hydroxyCoA dehydrogenase. These enzymes help convert fatty acids into acetyl-CoA, which enters the citric acid cycle to produce ATP, the energy currency of cells.

Key points:

• Fatty acid metabolism breaks down fatty acids for energy.
• The β-oxidation pathway is central to this process.
• Enzymes convert fatty acids into acetyl-CoA, eventually leading to ATP production.

electron_acceptors

In biochemical reactions, electron acceptors play a pivotal role. They gain electrons during oxidation-reduction reactions. In the context of β-oxidation, two key electron acceptors are involved: FAD and NAD⁺. Acyl-CoA dehydrogenase uses FAD as an electron acceptor, converting it into FADH₂. Meanwhile, β-hydroxyCoA dehydrogenase uses NAD⁺, reducing it to NADH. These reduced forms (FADH₂ and NADH) are later used in the electron transport chain, helping generate ATP.

Summarized:

• Electron acceptors are crucial for oxidation-reduction reactions.
• In β-oxidation, FAD and NAD⁺ serve as electron acceptors.
• FAD becomes FADH₂ and NAD⁺ becomes NADH, contributing to ATP production.

FAD and NAD+

Flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NAD⁺) are coenzymes essential for metabolic reactions. FAD participates in redox reactions by accepting electrons and becoming FADH₂, which can then donate these electrons to the electron transport chain. Similarly, NAD⁺ accepts electrons to become NADH. Both these coenzymes play a significant role in transferring electrons within cells, thereby aiding various metabolic pathways, including the β-oxidation of fatty acids.

Essential points:

• FAD and NAD⁺ are fundamental for metabolic reactions.
• FAD becomes FADH₂, and NAD⁺ becomes NADH after accepting electrons.
• Both coenzymes assist in cellular electron transfer, crucial for ATP production.