Purification, characterization, and gene cloning of lysyl aminoeptidase from Streptococcus thermophilus YRC001.
We purified and characterized an aminopeptidase from Streptococcus thermophilus YRC001 to obtain an enzyme for the application of reducing bitter-defect in cheese manufacturing. The purified enzyme was a monomer, and its molecular mass was estimated to be 90-100 kDa. It had a broad substrate specificity, and mostly hydrolyzed lysyl and leucyl peptides. The optimal temperature and pH for the enzyme were 35 degrees C and pH 6.5, respectively. EDTA, o-phenanthroline, and p-chloromercuribenzoate inhibited its activity, therefore it was considered to be a metallopeptidase. The purified enzyme efficiently reduced the bitterness of a trypsin digest of reconstituted skim milk. Therefore, we cloned a gene for the enzyme from YRC001. The nucleotide sequence of a 2,940-bp XbaI fragment containing the gene was analyzed. The gene encoded 849 amino acids, and the calculated molecular mass for the mature enzyme (initial methionine is removed) was 96,434. The deduced amino acid sequence showed high homology with the known bacterial lysyl aminopeptidase (aminopeptidase N).
Motoshima
Hidemasa
H
Research Center, Yotsuba Milk Products, Co., Ltd., 465-1 Wattsu, Kitahiroshima, Hokkaido 061-1264, Japan. research@yotsuba.co.jp
Shiraishi
Takayasu
T
Tsukasaki
Fuji
F
Kaminogawa
Shuichi
S
D000626:Aminopeptidases / Q000235:genetics*; D001483:Base Sequence; D002611:Cheese; D003001:Cloning, Molecular; D005511:Food Handling; D005798:Genes, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D013291:Streptococcus / Q000201:enzymology*; D013379:Substrate Specificity
D000626:Aminopeptidases; C056860:lysyl aminopeptidase