Open AccessIdentification and Characterization of Lipase Activity and Immunogenicity of LipL from Mycobacterium tuberculosis
Author(s) -
Jun Cao,
Guanghui Dang,
Huafang Li,
Tiantian Li,
Zhiguo Yue,
Na Li,
Yajun Liu,
Siguo Liu,
Liping Chen
Publication year - 2015
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0138151
Subject(s) - immunogenicity , lipase , immunogen , mycobacterium tuberculosis , biology , biochemistry , western blot , immune system , enzyme , chemistry , antibody , tuberculosis , genetics , gene , medicine , pathology , monoclonal antibody
Lipids and lipid-metabolizing esterases/lipases are highly important for the mycobacterial life cycle and, possibly, for mycobacterial virulence. In this study, we expressed 10 members of the Lip family of Mycobacterium tuberculosis . Among the 10 proteins, LipL displayed a significantly high enzymatic activity for the hydrolysis of long-chain lipids. The optimal temperature for the lipase activity of LipL was demonstrated to be 37°C, and the optimal pH was 8.0. The lipase active center was not the conserved motif G-x-S-x-G, but rather the S-x-x-K and GGG motifs, and the key catalytic amino acid residues were identified as G50, S88, and K91, as demonstrated through site-directed mutagenesis experiments. A three-dimensional modeling structure of LipL was constructed, which showed that the GGG motif was located in the surface of a pocket structure. Furthermore, the subcellular localization of LipL was demonstrated to be on the mycobacterial surface by Western blot analysis. Our results revealed that the LipL protein could induce a strong humoral immune response in humans and activate a CD8 + T cell-mediated response in mice. Overall, our study identified and characterized a novel lipase denoted LipL from M . tuberculosis , and demonstrated that LipL functions as an immunogen that activates both humoral and cell-mediated responses.