Characterization of secreted acid phosphatase activity of a streptomyces albus clinical isolate

Abstract

Due to limitations in the efficacy of the current vaccines against Tuberculosis, there are efforts currently underway exploring the possibility of using the phylogenetically related Streptomycetes as heterologous vaccine vehicles against Tuberculosis. Ideal candidates for such a vaccine should be somewhat pathogenic and physiologically similar to M. tuberculosis so as to induce an immune response capable of targeting and inactivating this pathogen. Towards establishing such a physiological relatedness, previous work in our laboratory has established a similarity profile between M. tuberculosis and a clinical isolate of Streptomyces albus at the level of secreted enzymes. Amongst these was a strong secreted acid phosphatase activity. This work reports on the characterization of the secreted acid phosphatase activity in this clinical isolate of Streptomyces albus. In this work, two enzymes with sequence homology to those encoding a protein tyrosine phosphatase and an inorganic pyrophosphatase were purified from the culture supernatant of S. albus. The calculated molecular masses of these two putative phosphatases were approximately 18 and 30 kDa, respectively. The S. albus protein tyrosine phosphatase has 50% amino acid sequence identity to the protein tyrosine phosphatase of M. tuberculosis (gi|686037535). The inorganic pyrophosphatase has 68% amino acid sequence identity with M. tuberculosis inorganic pyrophosphatase (gi|625006479). Based on our knowledge of the role of acid phosphatases in pathogenic bacteria, presence of this activity in the supernatant of S. albus further supports the physiological relatedness of M. tuberculosis and S. albus and supports the proposition of using S. albus as a heterologous vaccine against Tuberculosis.