Purification and characterization of a novel thermo stable L-methioninase from Streptomyces sp. DMMMH4 and its evaluation for anticancer activity

Abstract

L-methioninase has been purified 2.55-fold from the crude extract of Streptomyces sp. DMMMH4. The purification procedure was carried out by heat treatment and gel filtration on Sephadex G-200 column chromatography. SDS-PAGE electrophoresis showed a migrating protein band molecular mass of 47 kDa. The kinetic properties determined for the purified enzyme displayed optimum activity at 70°C and thermal stability were 70OC for 30 min. The enzyme showed maximum activity at pH 6 using acetate buffer 0.05M and was relatively stable across a broad range of pH values (5.5-8 pH). The enzyme strongly inhibited by Cr+2, Fe+2, Ni+2, Cd+2, PMSF, β-mercaptoethanol and SDS while Hg+2,Cu+2 and iodoacetate completely inhibited the enzyme activity at a final concentration of 10mM. The purified enzyme exhibited a Km of 0.7, 0.15 and 0.25 mM for L-methionine, DL-ethionine and L-cystine respectively. Cytotoxicity test demonstrate that enzyme was active against liver HepG2, breast MCF-7, lung A549, prostate PC3 and colon HCT116 cancer cell lines and has negligible toxicity toward a normal melanocyte cell line HFB4.