[Asparaginase mediated acid adaptation of mycobacteria].

Xiaolang Cai, Beibei Wu, Yang Fang, Houhui Song

Index: Wei Sheng Wu Xue Bao 52(12) , 1467-76, (2012)

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Abstract

Mycobacterium tuberculosis can survive inside host cells for a long time. To elucidate the acid adaptation mechanism mediated by the asparagine (Asn) metabolic pathway, the activity of asparaginase (AnsA) and growth of mycobacteria were characterized.The nonpathogenic M. bovis BCG was used as a model strain to characterize AnsA function. The recombinant AnsA was further expressed in E. coli, purified by Co2+ charged resin, and analyzed by enzymatic method. M. bovis BCG mutant (DansA) was constructed by homologous recombination. The growth and ammonia generation by M. bovis BCG wild type and mutant were evaluated in acidic medium.Ammonia was detected in the presence of AnsA and Asn. Deletion of ansA significantly delayed the growth of M. bovis BCG for 10 days in acidic medium. Asn was used by M. bovis BCG to produce ammonia, increasing pH.The acid adaptation of M. bovis BCG was mediated by ammonia, the metabolic product of asparagine. This provides new clue to uncover the survival mechanism of M. tuberculosis inside the acidic niche environment of host macrophage.