Production of heparin oligosaccharides by fusion protein of MBP–heparinase I and the enzyme thermostability

Enzymatic depolymerization of heparin to produce LMWH, a useful anticoagulant, has attracted much attention due to its mild reaction conditions and high selectivity. In this paper, we examined the feasibility of heparin depolymerization by heparinase I fused with maltose-binding protein (MBP) (MBP–HepA), which was functionally expressed in recombinant Escherichia coli with high activity. Our results showed that MBP–HepA degraded heparin effectively and the LMWHs with the weight average molecular weight (Mw) less than 3000 Da and narrow polydispersity were formed by controlling the reaction time. Thermostability of the fused enzyme was studied and possible mechanism for heat inactivation was proposed. The results showed that the MBP–HepA was relatively unstable and the enzyme inactivation was dependent on a third-order kinetics at the high temperature below 45 °C.