What is the Difference Between ATPase and ATP Synthase

The main difference between ATPase and ATP synthase is that ATPase is the enzyme, which breaks down ATP into ADP and free phosphate group. In contrast, ATP synthase is the enzyme, which synthesizes ATP by combining ADP and a free phosphate group. Furthermore, ATPase catalyzes a dephosphorylation reaction, which releases energy, but ATP synthase catalyzes a phosphorylation reaction, which stores energy. Moreover, most ATPases serve as transmembrane proteins, which move molecules across the membrane through primary active transport mechanisms. But, ATP synthase is located in the inner membrane of mitochondria, involving in oxidative phosphorylation. 

In brief, ATPase and ATP synthase are two enzymes with opposite functions in metabolizing ATP. Importantly, ATP is the main energy currency of the cell. 

Key Areas Covered 

1. What is ATPase
     – Definition, Occurrence, Importance
2. What is ATP Synthase
     – Definition, Occurrence, Importance
3. What are the Similarities Between ATPase and ATP Synthase
     – Outline of Common Features
4. What is the Difference Between ATPase and ATP Synthase
     – Comparison of Key Differences

Key Terms 

ATPase, ATP Synthase, Dephosphorylation, Oxidative Phosphorylation, Primary Active Transport

What is ATPase 

ATPase is the class of enzymes responsible for catalyzing the dephosphorylation of ATP. Hence, it decomposes ATP into ADP and a free phosphate ion. Furthermore, this dephosphorylation reaction of ATP releases energy, which drives another biochemical reaction. In general, most of the ATPase enzymes are coupled with integral membrane proteins, which move molecules across the membrane. Especially, ATPase-coupled carrier proteins undergo primary active transport.

Figure 1: Na⁺/K⁺ ATPase

Moreover, the above carrier proteins import many important metabolites necessary for cell metabolism and export wastes, toxins, etc. out of the cell. For example, Na⁺/K⁺ ATPase is a carrier protein that is important for the maintenance of cell membrane potential. Functionally, it transports three sodium ions out of the cell while transporting two potassium ions into the cell per hydrolyzed ATP molecule.  

What is ATP Synthase 

ATP is the enzyme responsible for the synthesis of ATP, the key energy storage molecule of the cell. Typically, the chemical reaction for the synthesis of ATP is given below. 

ADP + P_i + 3H⁺_out ⇌ ATP + H2O + 3H⁺_in  

Furthermore, ATP synthesis occurs in cellular respiration through an electrochemical gradient generated by protons across the mitochondrial membrane in a process called oxidative phosphorylation. Therefore, ATP synthase mainly occurs on the inner mitochondrial membrane. Besides during photosynthesis, ATP synthesis also occurs by a proton gradient generated across the thylakoid membrane in the light reaction.

Figure 2: ATP Synthase

Moreover, ATP synthase is an F-ATPase, which occurs in mitochondria, chloroplasts, and bacterial plasma membrane. They synthesize ATP using a proton gradient across the corresponding biological membranes. Also, F-ATPases contains two subunits; FO and F1, which has a rotational motor mechanism allowing for ATP production. Apart from that, F-ATPase is a type of rotary ATPase, which is one of the four types of ATPases. Here, the other three types of ATPases are P-ATPases, E-ATPases, and AAA proteins. 

Similarities Between ATPase and ATP Synthase 

• ATPase and ATP synthase are two enzymes, which take part in the metabolism of ATP, the main energy currency of the cell. 
• Therefore, they are responsible for transforming cellular energy between different biochemical processes of the cell. 
• Besides, both enzymes are integral membrane proteins anchored within biological membranes. 

Difference Between ATPase and ATP Synthase 

Definition 

ATPase refers to a class of enzymes, which catalyzes the decomposition of ATP into ADP and a free phosphate ion. In contrast, ATP synthase refers to the enzyme, which synthesizes the energy storage molecule, ATP. 

Type 

The four types of ATPases are the rotary ATPases, P-ATPases, E-ATPases, and AAA proteins.  Meantime, ATP synthesis is an F-ATPase, which is a type of rotary ATPases. 

Function 

ATPase breaks down ATP into ADP and a phosphate group, but ATP synthase synthesizes ATP. 

Type of Reaction 

ATPase undergoes dephosphorylation, but in contrast, ATP synthase undergoes phosphorylation. 

Occurrence 

ATPase occurs coupled with carrier proteins anchored to the biological membranes. But, ATP synthase is located in the inner membrane of mitochondria. 

Role 

ATPase participates in the primary active transport of molecules, but ATP synthase undergoes oxidative phosphorylation. 

Energy Metabolism 

ATPase releases energy from ATP, while ATP synthase stores energy in ATP. 

Conclusion 

In summary, ATPase is the enzyme responsible for the dephosphorylation of ATP into ADP and a phosphate group. Therefore, it releases energy stored in ATP. Also, ATPase occurs coupled with carrier proteins, which undergo primary active transport of molecules. In contrast, ATP synthase is the enzyme responsible for the synthesize of ATP through oxidative phosphorylation. Hence, it occurs in the inner membrane of mitochondria. Also, it stores the electrochemical energy of the proton gradient into ATP. On that account, the main difference between ATPase and ATP synthase is the role of the enzyme. 

References:

1. “ATPase.” Wikipedia, Wikimedia Foundation, 29 Feb. 2020, Available Here.
2. “ATP Synthase.” Wikipedia, Wikimedia Foundation, 29 Feb. 2020, Available Here.

Image Courtesy:

1.”Scheme sodium-potassium pump-en” By LadyofHats Mariana Ruiz Villarreal – Own work. (Public Domain) via Commons Wikimedia   
2. “ATP-Synthase” By Mitochondriale (Public Domain) via Commons Wikimedia