Ecological Questions 28 (2017) 4: 15–24 http://dx.doi.org/10.12775/EQ.2017.034 Identification and properties of a keratinase from Stenotrophomonas maltophilia N4 with potential application in biotechnology 8UV]XOD-DQNLHZLF]1* 0DJGDOHQD)UąN2 1'HSDUWPHQWRI%LRFKHPLVWU\)DFXOW\RI$JULFXOWXUHDQG%LRORJ\:DUVDZ8QLYHUVLW\RI/LIH6FLHQFHV±6**: Nowoursynowska 166 St, 02-787 Warsaw, Poland, e-mail: [email protected] 2)DFXOW\RI&LYLODQG(QYLURQPHQWDO(QJLQHHULQJ:DUVDZ8QLYHUVLW\RI/LIH6FLHQFHV±6**: Nowoursynowska 166 St, 02-787 Warsaw, Poland Received: 13 September 2017 /Accepted: 21 November 2017 $EVWUDFW The bacterium Stenotrophomonas maltophilia N4 produces different extracellular proteases when cultured in a mineral medium with 1% of bird feathers. One of the enzymes was purified and characterized. The studied enzyme is a peptidase with ke- ratinolytic activity. The optimal temperature for enzyme activity of the purified protein is 60°C, and its pH optimum 8.5. Its thermal VWDELOLW\LVDSSUR[LPDWHO\DIWHUWZRKRXUVRISUHLQFXEDWLRQDW&(Q]\PDWLFDFWLYLW\LVVWURQJO\LQKLELWHGE\')3DQG('7$ indicating that the enzyme belongs to the metal-dependent serine proteases. Calcium, magnesium and manganese ions enhance the activity of the studied keratinase. The enzyme has broad substrate specificity; it hydrolyzes not only keratin, but also casein, gelatin and hemoglobin Considering the fact that the N4 bacteria are capable of using bird feathers as a source of organic nitrogen and carbon, and bearing in mind the stability and the broad substrate specificity of the studied enzyme, it appears that it may find application in various branches of biotechnology. .H\ZRUGV extracellular protease, feather degradation, keratinase, enzyme purification, Stenotrophomonas maltophilia. ,QWURGXFWLRQ link amino acids together in the polypeptide chain forming a protein, may be used to remove protein waste, particu- larly including protein waste that is insoluble in water and Proteolytic enzymes, also known as peptidases, proteases therefore degrades more slowly in the natural environment. or proteinases, have always been a relevant and valid study .HUDWLQULFKE\SURGXFWVVXFKDVELUGIHDWKHUVKRUQVWKH subject. The considerable interest in bacterial proteolytic epidermis and the hair of animals, are an instance of such enzymes largely results from the possibilities of their ap- proteins with low hydrolytic susceptibility. They are a het- plication. Such enzymes are commonly used in biotech- erogeneous group of fibrous proteins with particularly nology due to their biochemical diversity, high stability low susceptibility to chemical and enzymatic hydrolysis under unfavorable reaction conditions, relatively low cost (Brandelli et al., 2010; Gupta & Ramnani, 2006; Gupta of obtaining, and the ease of their genetic manipulation et al., 2013). These proteins are resistant to hydrolysis be- 5DRHWDO6DZDQW 1DJHQGUDQ9RMFLFHWDO cause of their tight structure, which is supported primarily 2015). The enzymes, which hydrolyze peptide bonds that by cysteine bridges, and also by hydrogen bonds and hy- 16 Urszula Jankiewicz, Magdalena Frąk drophobic interactions (Bockle & Muller, 1997; Gopinath the feathers. The covert feathers of the helmeted guinea- et al., 2015). However, the interest of science in keratin fowl (Numida meleagris) were obtained from the Poultry hydrolysis relates not only to the effective removal of the Breeding Division at WULS. Before they were added to waste of insoluble protein polymers from the environment; the medium and autoclaved, the feathers were cleaned and it is also about the possibility of obtaining keratin, a valu- split into approximately 2 cm fragments. able cosmetic and pharmaceutical ingredient, that is at the .HUDWLQRO\WLFDFWLYLW\ZDVPHDVXUHGXVLQJDPRGLILHG center of researchers’ interest in this aspect (Lasekan et al., protocol by Cai et al. (2008) using 5 mg keratin azure as )RQWRXUDHWDO $WWHPSWVKDYHDOVREHHQPDGH the substrate suspended in 50 mM Tris-HCl buffer pH 8.5. to use keratin wastes as a source of bioactive peptides and Enzymatic reaction was carried out for 1 hour at 40°C with DJULFXOWXUDOIHUWLOL]HUV %UDQGHOOLHWDO .HUDWLQDVHV constant agitation at 200 rpm. One unit of keratinase activ- >(&@DUHUHVSRQVLEOHIRUWKHHQ]\PDWLFK\- ity (U) was the amount of enzyme that caused a change in drolysis of the discussed group of proteins. In addition to absorbance of 0.01 at 595 nm after reaction for 1 h. hydrolyzing fibrous proteins, keratinolytic enzymes also Caseinolytic activity was determined using the Anson hydrolyze collagen and non-fibrous proteins such as ca- method (1938) a with 1% casein solution in 50 mM Tris- sein and albumin, thus pointing to the enzymes’ broad sub- HCl buffer pH 8.0. The enzymatic reaction was carried out strate specificity (Gupta & Ramnani, 2006). A multitude for 30 min at the temperature of 40°C. One unit of caseino- of cysteine bridges in the keratin molecule suggests that lytic activity (U) was defined as the amount of enzyme re- sulfite reductases or reducing compounds participate in the quired to liberate 1 μmole of tyrosine within 30 min of the LQLWLDOVWDJHRIK\GURO\VLV .RUQLááRZLF].RZDOVND %R- reaction under the specified conditions. KDF]3UDNDVKHWDO .HUDWLQRO\WLFPLFURRU- ganisms include many types of microorganisms, including (Q]\PHSXULILFDWLRQDQGSURWHRPLFDQDO\VLVZLWK a large number of species from the genera: Bacillus, Strep- mass spectrometry (MS) tomyces, Lysobacter and Vibrio àDEDHWDO%UDQ- delli, 2008). The bacterium Stenotrophomonas maltophilia All protein purification stages were performed at the tem- is also capable of the effective degradation of bird feathers perature of 4°C. In order to obtain a clear supernatant, fil- and depilation of animal skins (Yamamura et al., 2002; tering and subsequent centrifugation (9000 x g for 10 min) Cao et al., 2009; Jeong et al., 2010). Stenotrophomonas were carried out on the third day of bacterial culture in maltophilia N4 is one of its strains; it has high proteolytic a mineral medium with 1% of bird feathers. The superna- activity and is the source of the enzyme that is discussed tant was precipitated using ammonium sulfate until 85% in this paper. saturation was reached. The protein precipitate obtained The main purpose of the study was to isolate and char- after centrifugation was then dissolved in 20 mM Tris-HCl acterize one of the proteolytic enzymes released by the buffer with pH 7.8 and dialyzed against the same buffer bacterium in terms of optimal activity, substrate specificity, for 12 hours, with two changes of the buffer. The prepara- the effect of inhibitors and metal ions. In order to evalu- tion after dialysis was separated on a column of DEAE– ate the usefulness of the protein in biotechnology, diverse Sepharose (Sigma), which was equilibrated with 20 mM substrates were used and the enzyme’s activity was studied Tris-HCl buffer pH of 8.0. Proteins that bound to the anion during its reaction in the presence of non-ionic detergents. exchanger were eluted in a gradient of 0 to 0.5 M NaCl. )UDFWLRQV PO YROXPH ZHUH VFUHHQHG IRU NHUDWLQRO\WLF and caseinolytic activity. The protein fractions that were 0DWHULDOVDQGPHWKRGV obtained after ion-exchange chromatography and had the highest activity were concentrated, resulting in approxi- %DFWHULDOFXOWXUHFRQGLWLRQVDQGHQ]\PH mately 30–50 μg/mL protein in the preparation. The pro- activity analysis tein samples previously digested with trypsin were sep- arated on a nanoAcquity UPLC (Ultra Performance LC) Stenotrophomonas maltophilia N4 (accession number: system and analyzed with an Orbitrap-based mass spec- AB667906) was the source of proteases in the presen- trometer (the Polish Academy of Sciences). The obtained ted study. Bacteria were grown for 72 h with shaking at results were analyzed using Blast software. 120 rpm and temperature 28ºC. Bacterial cultures were The fractions with highest keratinolytic activity were JURZQLQPLQHUDOPHGLXPFRPSRVHGRI JOLWHU .+2PO4, concentrated and then subjected to molecular sieve chro- .2HPO4, 3; MgSO41D&O)H&O3, 0.005. In order matography. The concentrated preparation (10-fold) was to optimize the composition of the culture medium, the fol- applied to a column of Superdex 200 (Sigma), which was lowing ingredients were used separately or in combinations equilibrated with 50 mM Tris-HCl buffer, pH 8.0. Active as supplements (g/L): feathers 10, yeast extract 2.5, Bacto fractions were used for characterizing the enzyme. Peptone 5, glucose 5. Control culture media did not contain Identification and properties of a keratinase from Stenotrophomonas maltophilia N4 with potential application 17 3URWHLQGHWHUPLQDWLRQDQG]\PRJUDSK\DQDO\VLV final concentration of 5.0 mM, after which the substrate was added and the activity tested. Protein concentration in samples was determined using the All results presented in this paper in the form of numer- method of Bradford (1976) with bovine serum albumin as ical values were means from 3 independent determinations. the protein standard. The mean error, reflecting maximal deviation of the results =\PRJUDPVZHUHREWDLQHGDIWHULQVHPLQDWLYH6'6 of measurements from the mean, did not exceed 5%. PAGE electrophoretic separation (without thermal de- QDWXUDWLRQ DQG ȕ ± PHUFDSWRHWKDQRO RI WKH VDPSOHV LQ 10% polyacrylamide SDS gel with incorporating 0.1% 5HVXOWV casein (Laemmli, 1970, with modifications). On comple- tion of electrophoresis the gels were incubated for 1 h in %DFWHULDOFXOWXUH 0.5% Triton X-100 solution, and then transferred to 100 DQGFRPSRVLWLRQRIJURZWKPHGLXP mM Tris-HCl