title: Characterization of a thiol-dependent endopeptidase from Lactobacillus helveticus CNRZ32.
abstract: An endopeptidase gene (pepE) was isolated from a previously constructed genomic library of Lactobacillus helveticus CNRZ32. The pepE gene consisted of a 1,314-bp open reading frame encoding a putative peptide of 52.1 kDa. Significant identity was found between the deduced amino acid sequence of pepE and the sequences for aminopeptidase C from Lactobacillus delbrueckii subsp. lactis DSM7290, L. helveticus CNRZ32, Streptococcus thermophilus CNRZ302, and Lactococcus lactis subsp. cremoris AM2. A recombinant PepE fusion protein containing an N-terminal six-histidine tag was constructed and purified to electrophoretic homogeneity. Characterization of PepE revealed that it was a thiol-dependent protease having a monomeric mass of 50 kDa, with optimum temperature, NaCl concentration, and pH for activity at 32 to 37 degrees C, 0.5%, and 4.5, respectively. PepE had significant activity under conditions which simulate those of ripening cheese (10 degrees C, 4% NaCl, pH 5.1). PepE hydrolyzed internal peptide bonds in Met-enkephalin and bradykinin; however, hydrolysis of alpha-, beta-, and kappa-caseins was not detected.
authors.affiliation: Department of Food Science, University of Wisconsin-Madison 53706, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Fenster
authors.forename: K L
authors.initials: KL
authors.lastname: Parkin
authors.forename: J L
authors.initials: JL
authors.lastname: Steele
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003545:Cysteine / Q000502:physiology; D010450:Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability; D005798:Genes, Bacterial / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011480:Protease Inhibitors; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D004791:Enzyme Inhibitors; D011480:Protease Inhibitors; D004744:Enkephalin, Methionine; D010450:Endopeptidases; C105450:PepE endopeptidase; D003545:Cysteine