Mori Sumiko, Miyamoto Maki, Kaneko Satoshi, Nirasawa Satoru, Komba Shiro, Kasumi Takafumi
Biological Function Division, National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
Arch Biochem Biophys. 2006 Oct 15;454(2):137-45. doi: 10.1016/j.abb.2006.08.001. Epub 2006 Aug 22.
The dipeptidases (PepVs) from three typical lactococcal strains, Lactococcus lactis subsp. lactis (L9), L. lactis subsp. cremoris (L6) and L. lactis subsp. hordniae (hT) were cloned and characterized. The metal-binding, catalytic, and substrate-binding sites are highly conserved among of them. A computer-generated three-dimensional model suggested that the amino acid differences between these PepVs were mostly located away from the active center. L9 PepV does not hydrolyze dipeptides bearing Pro or D-amino acid at the C-terminal amino acid. Unlike PepV from Lactobacillus delbrueckii, L9 PepV does not cleave beta-Asp-His, and has little ability to cleave dipeptides containing a beta-alanine. In addition, L9 PepV has a much higher kcat for dipeptides with an N-terminal Ala but a significantly higher Km when the N-terminal amino acid is Gly. The substrate recognition profile of PepV is further discussed on the basis of the kinetic analysis and the structural model.
对三株典型的乳酸乳球菌菌株，即乳酸乳球菌乳酸亚种（L9）、乳酸乳球菌乳脂亚种（L6）和乳酸乳球菌霍氏亚种（hT）的二肽酶（PepVs）进行了克隆和特性分析。它们的金属结合位点、催化位点和底物结合位点高度保守。计算机生成的三维模型表明，这些PepVs之间的氨基酸差异大多位于远离活性中心的位置。L9 PepV不会水解C端氨基酸带有Pro或D-氨基酸的二肽。与德氏乳杆菌的PepV不同，L9 PepV不会切割β-天冬氨酸-组氨酸，并且切割含有β-丙氨酸的二肽的能力较弱。此外，L9 PepV对N端为Ala的二肽具有更高的催化常数（kcat），但当N端氨基酸为Gly时，其米氏常数（Km）显著更高。基于动力学分析和结构模型，进一步讨论了PepV的底物识别特征。
