Construction of recombinant Escherichia coli for over-production of soluble heparinase I by fusion to maltose-binding protein

Heparinase I (EC 4.2.2.7) is one of the three heparinases purified from Flavobacterium heparinum that cleaves certain sequences of heparin/heparan sulfate specifically. Previous reports have shown that this enzyme expressed in recombinant Escherichia coli was highly prone to aggregate into inactive inclusion bodies even by fusion to cellulose-binding domain (CBD). In this paper, we fused heparinase I to maltose-binding protein (MBP) and expressed the fusion protein in E. coli to develop an expression system of soluble heparinase I. As a result, about 90% of the fusion protein (abbreviated as MBP-hepA) was soluble when expressed in the recombinant E. coli and the fusion protein could reach about 100 mg l−1 with an activity of 88.3 U l−1OD600−1. To our knowledge, this is the first time to produce soluble heparinase I at such a high yield.