Enzyme used in PCR is
High-Yield Explanation
In step 3 i.e polymerization : New DNA strands are synthesized by Taq polymerase. This enzyme is derived from bacteria Thermus acquaticus that are found in hot springs.Therefore the enzyme is not denatured at high temperature. REFERENCE : DM.VASUDEVAN.TEXTBOOK; SEVENTH EDITION; PAGE NO :638.