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Purification and Characterization of Intracellular Proteinase from Lactobacillus casei ssp. casei LLG

¹ Department of Food Science and Agricultural Chemistry, McGill University, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Quebec Canada H9X 3V9
² Department of Applied Animal Science, Sahmyook University, Seoul, Korea
³ Food Research & Development Centre, Agriculture and Agri-Food Canada, St-Hyacinthe, Quebec, Canada J2S 8E3

Corresponding author: B. H. Lee; e-mail: byong.lee{at}mcgill.ca.

The intracellular proteinase of Lactobacillus casei ssp. casei LLG was isolated in the cytoplasmic fraction with 0.05 M Tris-HCl buffer (pH 7.5). The enzyme was purified by the fast protein liquid chromatography system equipped with ion-exchange and gel filtration chromatographies. This proteinase comprised a single monomeric form and had a molecular weight of about 55 kDa and an isoelectric point near pH 4.9. The optimum pH and temperature for the enzyme activity were determined to be pH 6.5 and 37°C, respectively. The enzyme was inactivated by metal-chelating compounds (EDTA, 1,10-phenanthroline) and less affected by serine proteinase inhibitors (diisopropylfluorophosphate, phenylmethylsulfonyl fluoride). Proteinase activity was increased by Ca⁺⁺, Mn⁺⁺, and Co⁺⁺, and inhibited by Cu⁺⁺, Mg⁺⁺, and Zn⁺⁺. The activity of this enzyme to hydrolyze casein appeared to be more active on ß-casein than _s1-casein and -casein as monitored by polyacrylamide gel electrophoresis.

Key Words: Lactobacillus casei • proteinase • purification

Abbreviation key: LAB = lactic acid bacteria, NSLAB = nonstarter LAB

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