novel hyperactive hermes transposase mutants and genes encoding them are disclosed . these transposases are easily purified in large quantity after expression in bacteria . the modified hermes transposases are soluble and stable and exist as smaller active complexes compared to the native enzyme . the consensus target dna recognition sequence is the same as the native enzyme and shows minimal insertional sequence bias . these properties are useful in whole genome sequencing applications that involve sample dna preparation requiring simultaneous fragmentation and attachment of custom sequences to the ends of the fragments . methods and compositions using these transposases in fragmentation and 5 ′ end - tagging are also disclosed .