Biochemical characterisation of the coexisting tyrosinase and laccase in the soil bacterium Pseudomonas putida F6

• Published in: Enzyme and microbial technology Vol. 40; no. 5; pp. 1435 - 1441
• Main Authors: McMahon, Aoife M., Doyle, Evelyn M., Brooks, Sarah, O’Connor, Kevin E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 03-04-2007; Elsevier Science
• Subjects: Bacteria; Biological and medical sciences; Biotechnology; Fundamental and applied biological sciences. Psychology; Laccase; Pseudomonas putida; Pseudomonas putida F6; Tyrosinase; Pseudomonas putida F6; Tyrosinase; Laccase; Pseudomonadales; Soils; Enzyme; Pseudomonadaceae; Bacteria; Oxidoreductases; Monophenol monooxygenase; Pseudomonas putida
• ISSN: 0141-0229; 1879-0909
• DOI: 10.1016/j.enzmictec.2006.10.020

Two phenol oxidases, a tyrosinase and a laccase were isolated from cell extracts of the soil bacterium
Pseudomonas putida F6. Both oxidases were purified to homogeneity separately using a combination of anion exchange chromatography, gel filtration and gel slicing. The purified tyrosinase is a monomer with a relative molecular mass (
M
r) of approximately 39,000 while the purified laccase has a relative molecular mass (
M
r) of approximately 59,000. Maximum activity, for tyrosinase with
l-tyrosine (monophenolase) and
l-dopa (diphenolase) and for laccase with syringaldazine, was observed at 30
°C and pH 7.0. Both enzymes were stable over a broad range of temperatures and were most stable at 30
°C. Both the monophenolase and diphenolase activities of tyrosinase were relatively stable across a broad range of pH values with maximum stability at pH 5.0 and 4.0, respectively. Laccase was most stable at pH 7.0 with a narrow bell shaped curve over a range of pH values.
P. putida F6 tyrosinase has a 1.5-fold higher affinity for
l-tyrosine compared to
l-dopa. Furthermore
P. putida F6 tyrosinase exhibits a 2.7-fold higher affinity for α-methyl-
dl-tyrosine compared to α-methyl-
l-tyrosine.