The presently claimed and disclosed invention relates, in general, to dual action heparin synthases and, more particularly, to dual action heparin synthases obtained from Pasteurella multocida. The presently claimed and disclosed invention also relates to heparosan, heparin and heparin-like molecules provided by recombinant techniques and methods of using such molecules and also the identification or prediction of heparin synthases or component single action enzymes. The presently claimed and disclosed invention also relates to methods, and molecules produced according to such methods, for using the presently claimed and disclosed heparosan and/or heparin synthase for polymer grafting and the production of non-naturally occurring chimeric polymers incorporating stretches of one or more acidic GAG molecules, such as heparin, chondroitin, hyaluronan, and/or heparosan.