Purification and stability characteristics of an extracellular alkaline serine protease from a newly isolated Stenotrophomonas maltophiliastrain D2

摘要

One bacterial strain D2 (GenBank accession number CGMCC No. 1868) with a taxonomic affiliation to?Stenotrophomonas maltophilia?was isolated from the QINGDAO coast in China and can produce extracellular alkaline?protease. In this study, the alkaline protease was purified 4.9-fold by?a?four-step purification protocol with 33% activity recovery and was designed?S. maltophilia?Protease-D2?(SmP-D2).?The molecular weight of the protease was approximately 42 kDa?viewed?by sodium dodecyl sulfate polyacrylamide gel electrophoresis?(SDS-PAGE). The purified?D2?protease exhibitedstability over pH?6–11 and in the?temperature range?of?0-60°C with?optimal?activity?at pH 9and?60°C, respectively. The activity of the enzyme was?enhanced?with?Cu2+,?Ca2+,?and K+respectively, while?Ag+?and Mg2+?had little effect on the enzyme activity. The activity of the enzyme?inhibited by ethylene diamine tetra acetate (EDTA) and phenylmethanesulfonyl fluoride (PMSF),?indicating its serine type. However, the purified enzyme displayed significant stability to dithiothreitol (DTT),?urea and ethanol. The enzyme activity was moderate in the presence of anionic (SDS).?The N-terminal?amino acid sequence of two selected tryptic peptides was determined?as?NH2-AHGFLPLTK?and NH2-APSATGGSALYPLEFVVGK,?respectively,?by?electrospray ionization tandem mass spectrometry (ESI-MS/MS).?The?extremely high optimal?pH and moderate thermaltolerance tolerance?of?the alkaline serine?protease SmP-D2?suggested it?may be potential for use?as a biocatalyst in industry.