Enhancement of oxidative stability of the subtilisin nattokinase by site-directed mutagenesis expressed in Escherichia coli.

Nattokinase (subtilisin NAT, NK) is a bacterial serine protease with strong fibrinolytic activity and it is a potent cardiovascular drug. In medical and commercial applications, however, it is susceptible to chemical oxidation, and subsequent inactivation or denaturation. Here we show that the oxidative stability of NK was substantially increased by optimizing the amino acid residues Thr(220) and Met(222), which were in the vicinity of the catalytic residue Ser(221) of the enzyme.

[Progress in regulatory T cells research].

Regulatory T cells (Treg) are functionally mature T cell subpopulations which are key players of maintaining the balance of immunological defense system. Treg can proliferate in vivo or in vitro by antigen specific way or non-antigen specific way, and actively control the properties of other immune cells by suppressing their functional activity and their proliferation as well.