Abstract: The present invention is directed to nucleic acid and amino acid sequences of a novel piggyBac transposase enzymes created by modifying the transposase of Trichoplusia ni. The piggyBac transposases of the present invention are functionally active or hyperactive for excision and have decreased integration activity compared to wild type Trichoplusia ni piggyBac transposase enzyme. These transposases are ideal for use in methods of transforming cells and organisms. In particular embodiments, the present invention provides methods of transient integration and expression of transgenes.