Objective To explore the possible immunological mechanism of laminarin sulfate in the prevention of experimental atherosclerosis. Methods Serum soluble interleukin 2 receptor (sIL-2R) , circulating immuno-complex, sub units of T lymphocyte, inter leukin-6(IL-6) , in-terleukin-8(IL-8), tumor necrosis factor-a (TNF-a) and lipid metabolism were determined by ELISA, RIA in rats and quails. Results The lipid metabolism and immunologic function were prominent disturbance in animals after feeding with high-lipid food. However, Laminarin sulfate has obvious regulating effects on above-mentioned index. Conclusions The mechanism of laminarin sulfate in the prevention of atherosclerosis might be closely related to the regulation of the disturbance of lipid metabolism and to the regulation of the immunologic function of the body.

Enterokinase is a class of serine proteases that specifically recognize the cleavage DDDDK sequences. Therefore, enterokinase has been widely used as a tool enzyme in the field of biomedicine. Currently, the expression level of enterokinase in Pichia pastoris is low, which hinders related practical applications. In this study, the effects of six different signal peptides SP1, SP2, SP3, SP4, SP7 and SP8 on the secretory expression of enterokinase in Pichia pastoris were studied. Compared with α-factor, SP1 significantly increased the secretory expression of enterokinase (from 6.8 mg/L to 14.3 mg/L), and the enterokinase activity increased from (2 390±212) U/mL to (4 995±378) U/mL in shaking flask cultures. On this basis, the enterokinase activity was further enhanced to (7 219±489) U/mL by co-expressing the endogenous protein Kex2. Moreover, the activity that the mutant strain with N-terminal fusion of three amino acids of WLR was increased to (15 145±920) U/mL with a high specific activity of (1 174 600±53 100) U/mg. The efficient secretory expression of enterokinase laid a foundation for its applications in near future.