Lactococcus aminopeptidase

Application and Principle This procedure is used to determine leucine aminopeptidase activity in enzyme preparations derived from Lactococcus lactis. The assay is based on the rate of absorbance change over 5 min at 30° the change in absorbance is due to liberatedp-nitroaniline from the hydrolysis of leucine p-nitroanilide. 

Kiefer-Partch, B., Bockelman, W., Geis, A., and Teuber, M. (1989). Purification of a X-propyl-dipeptidyl aminopeptidase from the cell wall proteolytic system of Lactococcus lactis subsp. cremoris. Appl. Microbiol. Biotechnol. 31, 75-78. 

Neviani, E., Boquien, C. Y., Monet, V., Phan Thanh, L., and Gripon, J.-C. (1989). Purification and characterization of an aminopeptidase from Lactococcus lactis subsp. cremoris AM2. Appt. Environ. Microbiol. 55, 2308-2314. 

Niven, G. W. (1991). Purification and characterization of aminopeptidase A from Lactococcus lactis subsp. lactis NCDO 712. J. Gen Microbiol. 137,1207-1212. 

Christensen, J.E., Johnson, M.E., and Steele, J.L. (1995) Production of Cheddar cheese using a Lactococcus lactis ssp. cremoris SKll derivative with enhanced aminopeptidase activity. Int. Dairy /., 5, 367-379. 

Methods for eliminating bitter peptides in partial protein hydrolysates are known, but they cause a significant loss of essential amino acids. These procedures usually include additional enzymatic hydrolysis under controlled conditions (a shorter time for the hydrolysis leads to higher peptides that are not bitter) and a selection of suitable proteases, such as aminopeptidases, carboxypeptidases and some other proteases. Enzymes of plant and microbial origin have been successfully used for this purpose. For example, the intracellular peptidases from Lactococcus lactis ssp. cremoris and Brevibacterium linens, which have high proteolytic activity, successfully hydrolyse bitter peptides in cheeses. 

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