生物素羧基载体蛋白英文名

Biotin Carboxyl Carrier Protein: The Unsung Hero of Cellular Metabolism

If you’ve found your way here by searching for “Biotin Carboxyl Carrier Protein,” you’re likely delving into the intricate world of biochemistry, cellular metabolism, or perhaps researching a specific academic topic. This specialized term points to a deep and specific curiosity. To fully address your quest for knowledge, this article will provide a comprehensive overview of this critical protein, explaining its function, importance, and context within the cell.

What is Biotin Carboxyl Carrier Protein?

Let’s start with the basics. The English name for 生物素羧基载体蛋白 is Biotin Carboxyl Carrier Protein, universally abbreviated as BCCP.

BCCP is not a standalone enzyme but an essential protein domain or subunit that forms a core part of larger enzyme complexes. Its primary role is to serve as a mobile “swinging arm” that shuttles intermediates between different active sites within a multi-enzyme complex. It does this by being covalently attached to a small, vital cofactor: biotin (also known as Vitamin B7).

The Core Function: A Molecular Taxi Service

The name “Biotin Carboxyl Carrier Protein” perfectly describes its job:

1. Carrier: It carries the biotin molecule.
2. Carboxyl: It carries a carboxyl group (-COOH or COO⁻) that is temporarily attached to the biotin.

In essence, BCCP is a molecular taxi. The “passenger” is the biotin molecule, which itself picks up and drops off a carboxyl group during critical biochemical reactions. This process is fundamental to a class of reactions known as ATP-dependent carboxylations.

Where is BCCP Found and What Does It Do?

BCCP is most famously a component of two crucial multi-enzyme complexes:

1. Acetyl-CoA Carboxylase (ACC)
This is where BCCP plays its most well-studied role. ACC is the first and rate-limiting enzyme in the synthesis of fatty acids.

• The Process:
  • Step 1 (Carboxylation of Biotin): The BCCP-biotin complex swings to the first active site, the biotin carboxylase (BC) domain. Here, using ATP for energy, a carboxyl group is added to the biotin molecule, forming carboxybiotin.
  • Step 2 (Transfer of the Carboxyl Group): The “loaded” BCCP-biotin arm then swings to a second active site, the carboxyltransferase (CT) domain. Here, the carboxyl group is transferred from biotin to its target molecule, acetyl-CoA, converting it into malonyl-CoA.
• Biological Significance: Malonyl-CoA is the fundamental building block for producing long-chain fatty acids. Therefore, without a functional BCCP, fatty acid synthesis grinds to a halt. This makes ACC, and by extension BCCP, a key regulatory point in metabolism and a potential target for treating conditions like obesity and cancer.

2. Propionyl-CoA Carboxylase (PCC)
PCC functions in a very similar manner but operates in a different metabolic pathway: the breakdown of certain amino acids and odd-chain fatty acids.

• The Process: The mechanism is analogous to ACC. BCCP carries a carboxyl group to propionyl-CoA, converting it to methylmalonyl-CoA.
• Biological Significance: This is a critical step in the gluconeogenic pathway and energy production. Deficiencies in PCC can lead to a severe metabolic disorder called propionic acidemia.

Why is BCCP So Important?

The unique design of BCCP provides several key advantages to the cell:

• Channeling of Intermediates: By physically carrying the reactive carboxyl group between active sites, BCCP prevents the release of unstable intermediates into the cellular milieu. This increases the efficiency and speed of the reaction.
• Spatial Organization: It allows a single enzyme complex to perform two distinct chemical steps at separate active sites without the substrates diffusing away.

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• Metabolic Regulation: As a core component of ACC, BCCP is indirectly involved in the hormonal and dietary regulation of fatty acid synthesis. When the body needs to make fats, this system is activated.

Summary and Key Takeaways

• Name: Biotin Carboxyl Carrier Protein (BCCP).
• Identity: A protein domain that is permanently attached to a biotin cofactor.

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• Function: Acts as a mobile carrier to transport a carboxyl group between the active sites of large enzyme complexes like Acetyl-CoA Carboxylase (ACC) and Propionyl-CoA Carboxylase (PCC).
• Role in Metabolism: It is indispensable for fatty acid synthesis (via ACC) and the metabolism of specific amino acids and fats (via PCC).
• Broader Implication: Understanding BCCP is fundamental to grasping how cells efficiently manage complex, multi-step biochemical transformations, and it highlights the critical role of vitamins (like biotin) in human health and disease.