Isolation and Characterization of Novel Tyrosinase from Laceyella sacchari

We here describe the isolation and characterization of a tyrosinase from a newly isolated soil bacterium. 16S rDNA sequence analysis revealed that the bacterium most probably belongs to the species Laceyella sacchari (Ls) (>99.9% identity). The tyrosinase extracellular enzymatic activity was induced in the presence of L-methionine and CuSO4. The crude enzyme was first purified by centrifugation followed by ammonium sulphate precipitation and ultrafiltration. After removal of a brown pigment, probably melanin, a purified enzyme was obtained by further separation of the crude protein mixture using size exclusion chromatography. Some 10.5 mg of pure tyrosinase (LsTyr) was isolated with a molecular mass of 30 910 Da, based on MALDI mass spectrometry. Together with the observed enzymatic activity, N-terminal chemical sequence analysis confirmed that the isolated enzyme is homologous to other tyrosinases. The kinetic parameters for the diphenol substrates L-DOPA and dopamine and for the monophenol substrate L-tyrosine were determined to be K-M = 4.5 mM, 1.5 mM and 0.055 mM, and k(cat)/K-M = 261.5 mM (1) s (1), 30.6 mM (1) s (1) and 56.3 mM(-1) s(-1), respectively. Maximal activities of the purified enzyme were found to occur at pH 6.8.