title: Extraction and partial characterization of proteolytic activities from the cell surface of Lactobacillus helveticus Zuc2.
abstract: Proteolytic activities were extracted from a dairy Lactobacillus helveticus strain and partially characterized. A first cell envelope proteinase (CEP) was extracted using a high ionic strength buffer, both in the presence and in the absence of Ca2+. Moreover, cell treatment by 5 M LiCl allowed for the selective removal of the S-layer protein and CEP, suggesting an enzyme ionic linkage to the cell envelope similar to that observed for the Slayer structure. The enzyme specificity against alpha(s1)-CN (f1-23) showed unusual activity on the Lys3-His4 bond compared with other proteinases of the same species. A second proteinase appeared to be linked to the cell membrane because it was extractable only after membrane disgregation by detergents. Its specificity against CN fractions and alpha(s1)-CN (f1-23) was different from that of the first CEP; moreover, the measured activity was lower than that of CEP.
authors.affiliation: Istituto Microbiologia, Università Cattolica del Sacro Cuore, via Emilia parmense, 84, 29100 Piacenza, Italy. gianluigi.scolari@unicatt.it
authors.forename: G
authors.initials: G
authors.lastname: Scolari
authors.forename: M
authors.initials: M
authors.lastname: Vescovo
authors.forename: C
authors.initials: C
authors.lastname: Zacconi
authors.forename: F
authors.initials: F
authors.lastname: Vescovi
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002458:Cell Fractionation / Q000379:methods; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006868:Hydrolysis; D052198:Lactobacillus helveticus / Q000201:enzymology*; D018021:Lithium Chloride / Q000494:pharmacology; D008565:Membrane Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D010447:Peptide Hydrolases / Q000737:chemistry / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D010447:Peptide Hydrolases; D018021:Lithium Chloride