Site-specific, covalent immobilization of BirA by microbial transglutaminase: A reusable biocatalyst for in vitro biotinylation.

A facile approach for the production of a reusable immobilized recombinant Escherichia coli biotin ligase (BirA) onto amine-modified magnetic microspheres (MMS) via covalent cross-linking catalyzed using microbial transglutaminase (MTG) was proposed in this study. The site-specifically immobilized BirA exhibited approximately 95% of enzymatic activity of the free BirA, and without a significant loss in intrinsic activity after 10 rounds of recycling (P > 0.05). In addition, the immobilized BirA can be easily recovered from the solution via a simple magnetic separation. Thus, the immobilized BirA may be of general use for in vitro biotinylation in an efficient and economical manner.