title: Cloning and sequencing of the gene encoding X-prolyl-dipeptidyl aminopeptidase (PepX) from Streptococcus thermophilus strain ACA-DC 4.
abstract: OBJECTIVE
  To clone and sequence the pepX gene from Streptococcus thermophilus.
  
  
  RESULTS
  Three pairs of primers were used in polymerase chain reactions using as template the total DNA from Strep. thermophilus ACA-DC 4 in order to amplify, clone and sequence the pepX gene. Sequence analysis revealed an open reading frame of 2268 nucleotides encoding a protein of 755 amino acids. The calculated molecular mass of 85 632 Da agreed well with the apparent molecular mass of 80 000 Da previously determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and gel filtration for the monomeric form of the purified enzyme.
  
  
  CONCLUSIONS
  The pepX gene from Strep. thermophilus ACA-DC 4 was cloned and sequenced. The PepX protein showed significant sequence similarity with PepX enzymes from other lactic acid bacteria and contained a motif which was almost identical with the active site motif of the serine-dependent PepX family.
  
  
  CONCLUSIONS
  There are economic and technological incentives for accelerating and controlling the process of cheese ripening. To achieve this, starters may be modified by introducing appropriate genes from other food-grade bacteria. New or additional peptidase activities may alter or improve the proteolytic properties of lactic acid bacteria.
authors.affiliation: Laboratory of Dairy Research, Department of Food Science and Technology, Agricultural University of Athens, Greece.
authors.forename: R
authors.initials: R
authors.lastname: Anastasiou
authors.forename: M
authors.initials: M
authors.lastname: Papadelli
authors.forename: M D
authors.initials: MD
authors.lastname: Georgalaki
authors.forename: G
authors.initials: G
authors.lastname: Kalantzopoulos
authors.forename: E
authors.initials: E
authors.lastname: Tsakalidou
mesh_terms: D002611:Cheese / Q000382:microbiology*; D003001:Cloning, Molecular; D017931:DNA Primers; D004269:DNA, Bacterial / Q000032:analysis; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000235:genetics*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013291:Streptococcus / Q000145:classification / Q000201:enzymology* / Q000235:genetics*
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C098392:PepX dipeptidyl aminopeptidase