Simplify the following text for a Grade 8 native English-speaking person.
Original: ATP synthase is an enzyme found in cells that make ATP from ADP and inorganic phosphate . The ATP synthase is powered by the difference of concentration of pH between inside and outside the place where the enzyme is located .
Simplified: E. coli ATP synthase is the simplest known form of ATP synthase , with 8 different subunit types .