ABSTRACT
Amidases, also known as amidohydrolases (EC 3.5.1.4), are enzymes within the nitrilase superfamily or amidase signature family. They hydrolyze amides and nitriles into their corresponding acids while releasing ammonia. These enzymes are widely used in biotechnology and industry. However, their production is limited to a few organisms, which cannot meet industrial demand. Therefore, exploring new amidase sources is crucial. This study focuses on purifying and characterizing amidase from Aspergillus fumigatus using cold acetone precipitation and column chromatography with Sephadex G-100. The effects of temperature, pH and metal ions, on the enzyme activity were examined for both crude and purified amidase. The thermal and pH stability of the enzyme alongside the enzyme kinetics were also assessed. The purified amidase exhibited optimal activity of 13.1 U/mL at 70°C, with 65% residual activity after 5 hours at this temperature. The pH studies showed optimal activity at pH 5.0 for the purified enzyme (7.8 U/mL) and at pH 4.0 for the crude enzyme (5.5 U/mL). Metal ion effects indicated that Zn²?, Mg²?, and EDTA enhanced, while Cu²? inhibited, the activities of both crude and purified amidase. Kinetic analysis showed that the enzyme followed Michaelis-Menten kinetics, with Km and Vmax values of 0.104 mM and 1.884 U/mL for crude amidase, and 0.017 mM and 1.872 U/mL for purified amidase. These findings suggest that amidase from Aspergillus fumigatus holds potential for industrial applications where amidases are essential.
ABSTRACT
Objective To develop mycobacterial inducible expression vectors which permit to overexpress Mycobacterium tuberculosis (Mtb) immunodominant antigen, and to analyze its immunogenicity after purification by affinity chromatography. Methods The regulatory region of M. smegmatis (Ms) acet-amidase(pACE) was obtained by PCR amplification, and was used as promoter to construct the mycobacteri-al inducible expression vectors, pMF series. The coding gene of Mtb chimeric antigen Ag856A2 which is a recombinant Ag85A with 2 copies of ESAT-6 inserted in its Acc Ⅰ site and showed excellent immunogenicity in the animal experiments we described previously, was cloned into the pMF vector series, and was induced to express by the addition of acetamide. The recombinant protein expressed in the Ms was purified by the Ni~(2+)-NTA affinity chromatography, the resulted homologous recombinant antigen was added into the spleen cells separated from BCG vaccinated mice, and the immunogenicity was analyzed by the IFN-γ ELISPOT as-say. Results The mycobacterial inducible expression vectors, pMF series was constructed successfully, target antigen could be. induced to express in the Ms by the addition of 0.02% acetamide, and could be puri-fied by the Ni~(2+) -NTA affinity chromatography due to the addition of 6×His tag in the vector pMF406. Fur-thermore, the mycobactefial homologous antigen could induce more IFN-γ secretion than the heterogonous one. Conclusion The mycobacterial inducible expression system based on the regulatory region of Ms acet-amidase as promoter could permit the Mtb target antigen of interest overexpression and purification, and the immunogenicity of the homologous antigen from Ms is better than that of be expressed from E. coli, which may be more potential for immunological detection of tuberculosis.