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In enzymology, a chloroplast protein-transporting ATPase (EC 3.6.3.52) is an enzyme that catalyzes the chemical reaction ATP + H 2 O ⇌ {\displaystyle \rightleftharpoons } ADP + phosphate Thus, the two substrates of this enzyme are ATP and H 2 O , whereas its two products are ADP and phosphate .
ADP and Pi (inorganic phosphate) bind spontaneously to the three β subunits of the F 1 domain, so that every time it goes through a 120° rotation ATP is released (rotational catalysis). The F o domains sits within the membrane, spanning the phospholipid bilayer, while the F 1 domain extends into the cytosol of the cell to facilitate the use ...
In plants, ATP synthase is also present in chloroplasts (CF 1 F O-ATP synthase). The enzyme is integrated into thylakoid membrane; the CF 1-part sticks into stroma, where dark reactions of photosynthesis (also called the light-independent reactions or the Calvin cycle) and ATP synthesis take place. The overall structure and the catalytic ...
The thylakoid ATP synthase is a CF1FO-ATP synthase similar to the mitochondrial ATPase. It is integrated into the thylakoid membrane with the CF1-part sticking into the stroma. Thus, ATP synthesis occurs on the stromal side of the thylakoids where the ATP is needed for the light-independent reactions of photosynthesis.
A diagram depicting newly discovered molecules (PTOX and the NDH complex) as part of the chlororespiratory process in higher order plants like Rosa Meillandina. In the year 2002, the discovery of the molecules; plastid terminal oxidase (PTOX) and NDH complexes have revolutionised the concept of chlororespiration. [ 2 ]
Some ATPases work in reverse, using the energy from the hydrolysis of ATP to create a proton gradient. There are different types of ATPases, which can differ in function (ATP synthesis and/or hydrolysis), structure (F-, V- and A-ATPases contain rotary motors) and in the type of ions they transport. [3] [4] The types with this domain include:
The energy resulting from the flux of protons back into the matrix is used by ATP synthase to combine inorganic phosphate and ADP. [6] [2]: 743–745 Similar to the electron transport chain, the light-dependent reactions of photosynthesis pump protons into the thylakoid lumen of chloroplasts to drive the synthesis of ATP. The proton gradient ...
The hydrogen ions are released in the thylakoid lumen and therefore contribute to the transmembrane chemiosmotic potential that leads to ATP synthesis. Oxygen is a waste product of light-dependent reactions, but the majority of organisms on Earth use oxygen and its energy for cellular respiration , including photosynthetic organisms .