Yarrowia lipolytica YlTun15 (GeneBank Acc. N° MF327143), isolated from farmed Dicentrarchus labrax’s gills, secretes an alkaline extracellular protease, which exhibited the highest activity at pH 9 and temperature 45°C. The enzyme activity extracted was tested in the presence of different ion metal and protein inhibitors. The enzyme activity increased in the presence of both Cu2+ (1 mM) and Mn2+ (5mM) in the medium. K+, Na2+, Mg2+ and Ca2+ had no effect on the enzyme activity while Ni+, Hg+, Zn2+ and Fe2+ decreased significantly its relative activity to 43.63%, 66.25%, 30.75% and 19.48% respectively at the 5 mM level. The enzyme was almost (activity=1.47%) inhibited by phenylmethylsulfonyl fluoride at the concentration of 5 mM. However, the protease activity was relatively constant in the presence of EDTA and SDS that may conclude that this enzyme was not a metalloprotease and belong to the serine protease category. After 18 months-storage at -20°C, the enzyme activity has decreased to 23.17%. This protease may have a potential application in food and detergent activity.
Boutheina Bessadok, Mahmoud Masri, Thomas Breuck and Saloua Sadok*
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