Purification and characterization of thermostable serine proteases encoded by the genes ttha0099 and ttha01320 from Thermus thermophilus HB8

Heterologous expression and characterization of a novel subtilisin-like protease from a thermophilic Thermus thermophilus HB8

Subtilisins are a family of serine proteases used widely throughout the detergent, leather and food industries, with the identification and development of new enzymes holding much potential value. Thermus thermophilus HB8 was examined for serine proteases and found TTHA0724 gene. Sequence analysis of this putative serine protease placed it within the subtilisin family. To obtain active T. thermophilus HB8 subtilisins, three genes encoding prepro-subtilisin, pro-subtilisin and mature-subtilisin were cloned and expressed in Escherichia coli Transetta (DE3). Although direct expression of the mature-subtilisin gene was found to produce inactive inclusion bodies, expression of the pro-subtilisin gene resulted in active mature-subtilisin, indicating that the pro-sequence of translated pro-subtilisin underwent autoproteolysis. The resulting mature-subtilisin exhibited maximal activity between 65 and 85 °C at pH 7.5. The mature-subtilisin showed good stability, maintaining 50% activity after 48 h at 75 °C and >78% activity across the pH range 5.0-9.5. Furthermore, the mature-subtilisin demonstrated broad substrate specificity, with no requirement for the presence of metal ions which are essential for other subtilisin enzymes. Despite this Cu²⁺ was able to increase enzyme activity, while Ca²⁺ partially inhibited the activity. These properties suggest that T. thermophilus HB8 mature-subtilisin has potential value in its application in many industries.

Purification and partial characterization of a low molecular fibrinolytic serine metalloprotease C142 from the culture supernatant of Bacillus subtilis C142

Novel serine metalloprotease-like enzyme, C142 was purified from the culture supernatant of Bacillus subtilis C142. The C142 was purified to homogeneity by a two-step procedure with a 20.7-fold increase in specific activity and 0.9% recovery. The molecular mass of C142 was approximately 23.5kDa based on SDS-PAGE. The N-terminal amino acid sequence of the first 21 amino acids of C142 was AQSVPYGISQIKAPALHSQGY. Its optimum pH, optimum temperature, pH stability, and thermal stability were pH 6, 40°C, pH 6-8, and 20-35°C, respectively. C142 was strongly inhibited by PMSF and EGTA, suggesting that C142 was a serine metalloprotease-like enzyme. C142 showed the highest specificity toward the substrate for t-PA. The apparent K_m, V_max, and K_cat values of C142 toward H-d-Ile-Pro-Arg-pNA were determined as 0.34mM, 0.25mmolmg^-1min^-1, and 46.83s^-1. C142 exhibited fibrinolytic activity, which is stronger than that of plasmin. C142 hydrolyzed Aα, and Bβ-chains of fibrinogen, but did not cleave γ-chains. C142 had antithrombotic effect in three animal models. C142 was devoid of hemorrhagic activity at a dose of 20,000FU/kg. Taken together, our results indicate that B. subtilis C142 produces a serine metalloprotease-like enzyme/fibrinolytic enzyme and this enzyme might be used as a new thrombolytic agent.