DNA supercoiling means under or over winding of the DNA strand and basically is to become more condensed and more organized. Supercoiling is very important as it compacts the genetic code and as if that was not enough supercoiling also regulates and oversees the access the the genetic code.
Yes they can because the catalyst does not take part in the chemical reaction and remains unchanged after the reaction has ended. Biological catalysts are known to be recycled by the bodies in which they work.
