Enzyme method

A method of characterising a target polynucleotide, comprising:

• (a) contacting the target polynucleotide with a transmembrane pore, wherein a first helicase is bound to the target polynucleotide such that the first helicase controls the movement of the target polynucleotide through the pore;
• (b) further contacting the target polynucleotide with a second helicase as the first helicase controls the movement of the target polynucleotide through the transmembrane pore, wherein the second helicase binds to an internal polynucleotide of the target polynucleotide at a location on the polynucleotide different than where the first helicase is bound without concurrent binding to a terminal nucleotide of the target polynucleotide, and wherein the second helicase controls movement of the target polynucleotide through the pore after the first helicase disengages from the target polynucleotide;
• and
• (c) measuring one or more characteristics of the target polynucleotide during one or more interactions as the target polynucleotide moves through the transmembrane pore, wherein the one or more interactions are measured along a length of the target polynucleotide that comprises at least 500 nucleotides and exceeds processivity of the first helicase, thereby characterising the target polynucleotide.