title: Peptidase activity in various species of dairy thermophilic lactobacilli.
abstract: OBJECTIVE
  The aim of the present work was to evaluate the enzymatic potential manifested by aminopeptidase activity of different thermophilic Lactobacillus biotypes and to measure the influence of cell growth phase on enzyme expression.
  
  
  RESULTS
  The activities were evaluated by the hydrolysis of beta-naphthylamide substrates for both whole and mechanically disrupted cells of L. helveticus, L. delbrueckii subsp. bulgaricus and L. delbrueckii subsp. lactis strains, collected from both the exponential and the stationary growth phase. In general, activities were higher for cells in the exponential rather than in the stationary phase and the disrupted cells showed higher activities than the whole cells. The highest activity expressed by all strains corresponded to X-prolyl-dipeptidyl aminopeptidase while a moderate activity was observed towards Arg-betaNa, Lys-betaNa and Leu-betaNa. The lowest activity was observed for Pro-betaNa.
  
  
  CONCLUSIONS
  It may be inferred that the cell structure and the cell physiology are crucial to define the level of efficiency of expression for aminopeptidase activity. The two species may be characterized by a different enzymatic system that hydrolyses N-terminal leucine.
  
  
  CONCLUSIONS
  The differences of peptidase activities in L. helveticus and L. delbrueckii species acquires an importance to comprehend their role in the biochemical events occurring in cheese ripening.
authors.affiliation: Istituto Sperimentale Lattiero-Caseario, Lodi, Italy Dipartimento di Genetica Antropologia Evoluzione, Università degli Studi di Parma, Parma, Italy. mgatti@ilclodi.191.it
authors.forename: M
authors.initials: M
authors.lastname: Gatti
authors.forename: M E
authors.initials: ME
authors.lastname: Fornasari
authors.forename: C
authors.initials: C
authors.lastname: Lazzi
authors.forename: G
authors.initials: G
authors.lastname: Mucchetti
authors.forename: E
authors.initials: E
authors.lastname: Neviani
mesh_terms: D000626:Aminopeptidases / Q000378:metabolism*; D003470:Culture Media; D003611:Dairy Products / Q000382:microbiology*; D005516:Food Microbiology; D006868:Hydrolysis; D007778:Lactobacillus / Q000201:enzymology*; D008828:Microbiological Techniques / Q000379:methods; D013053:Spectrophotometry / Q000379:methods
chemical_list: D003470:Culture Media; D000626:Aminopeptidases; C022750:X-Pro aminopeptidase