ATPases are a class of enzymes that catalyze the decomposition of ATP into ADP and a free phosphate ion. This dephosphorylation reaction releases energy, which the enzyme (in most cases) harnesses to drive other chemical reactions that would not otherwise occur. This process is widely used in all known forms of life. GTPases (singular GTPase) are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases.
An Overview of ATPase/GTPase
ATPase, also known as adenosine triphosphatase, is an enzyme that catalyzes the hydrolysis of adenosine triphosphate (ATP) to adenosine diphosphate (ADP) and free phosphate ions. This catalytic chemical reaction is an exothermic reaction, that is, the reaction process releases energy. ATPase uses this energy to drive chemical reactions. GTPase is a kind of hydrolase that can bind to and hydrolyze guanosine triphosphate (GTP). GTP binding and hydrolysis occur in the highly conserved G domains shared by all GTPases. GTPases promote protein biosynthesis at ribosomes, promote control and differentiation during cell division, promote protein transport through membranes, and transport intracellular vesicles.
Major type of ATPase/GTPase
ATPases can be classified into F-ATPase, V-ATPase, A-ATPase, and E-ATPase depending on the differences of their functions, structures, and types of transport ion. F-ATPase is present in the mitochondria, chloroplasts and bacterial plasma membranes. It is the main producer of ATP. F-ATPase uses a proton gradient produced by oxidative phosphorylation (mitochondria) or photosynthesis (chloroplast). V-ATPase is mainly located in eukaryotic vacuoles. It catalyzes the hydrolysis of ATP to transport solutes and lower the pH in organelles, such as lysosomal proton pumps. A-ATPase is present in archaea and its function is similar to that of F-ATPase. P-ATPase is present in bacterial, fungal and eukaryotic plasma membranes and organelles. The role of P-ATPase is to transport a variety of different ions across the membrane.
ATPase/GTPase and diseases
Ca2+ ATPase is an ATP-dependent calcium pump that drives intracellular calcium ion out of the cell. Its abnormal expression will lead to disorders of intracellular calcium ion balance and various diseases. Because calcium ion is closely related to neurotransmission and muscle contraction, early studies mostly focused on the central nervous system and cardiovascular system. Studies found that changes in Ca2+ ATPase expression in various malignancies, including breast cancer, colorectal cancer, and pancreatic cancer. At the same time, the presence and differential expression of various subtypes of Ca2+ ATPase were found and confirmed in some malignant cell lines.
Leipe D.D., Wolf Y.I., Koonin E.V., Aravind, L. (2002). Classification and evolution of P-loop GTPases and related ATPases. J. Mol. Biol. 317 (1): 41–72.