Part:BBa_K5398600

A tyrosinase enzyme TyrVs

Tyrosinase is a copper-containing oxidoreductase that possesses two catalytic activities, and is involved in the first few steps of melanin synthesis from l-tyrosine. As shown in Fig. 1, tyrosinase catalyzes the ortho-hydroxylation of l-tyrosine to l-DOPA via its monophenolase (MP) activity, and consecutively oxidizes l-DOPA to l-dopaquinone via the diphenolase (DP) activity, thereby consuming oxygen. l-dopaquinone is not stable and will be further non-enzymatically oxidized to l-dopachrome (a red-colored product) in the presence of O₂.TyrVs refers to a tyrosinase enzyme derived from Verrucomicrobium spinosum, which plays a critical role in the hydroxylation of tyrosine residues into L-Dopa. This enzyme has shown efficient activity, particularly in the context of biological adhesion, as demonstrated in studies co-expressing mussel foot protein 3 with TyrVs.

Fig. 1 Synthesis scheme of L-DOPA and further oxidized product L-dopachrome.

To validate the functionality of the tyrosinase TyrVs, we designed bacteria expressing TyrVs.We constructed the pET-SUMO-TyrVs vector, after culturing at 16°C for 20 hours, extracted the proteins for SDS-PAGE and Coomassie Brilliant Blue staining analysis.

Fig. 2 Protein pre-expression of SUMO-TyrVs(52.2 kDa).

Lane 7: TyrVs-Whole Cell Lysate(+IPTG). Lane 8: TyrVs-Supernatant(+IPTG). Lane 9: TyrVs-Pellet(+IPTG). Lane 10: TyrVs-Whole Cell Lysate(CK). Lane 11: TyrVs-Supernatant(CK). Lane 12: TyrVs-Pellet(CK).

We purified SUMO-TyrVs using a HiTrap Ni-NTA column. The purified protein was verified by SDS-PAGE and was found to be present in the 50 mM imidazole elution fraction.

Fig. 3 Protein expression of SUMO-TyrVs(52.2 kDa).

Lane 1: Marker. Lane 2: Lysis Buffer. Lane 3: Supernatant. Lane 4: 20 mM Imidazole. Lane 5: 50 mM Imidazole. Lane 6: 150 mM Imidazole.

We conducted tests on the reactions from tyrosine to dopaquinone and from L-DOPA to dopaquinone. The experiment of enzymatic reaction from tyrosine to dopaquinone was conducted at 37°C with an enzyme concentration of 0.1 μg/mL. The calculated Michaelis constant (Km) and maximum velocity (Vmax) were 456.8 μmol/L and 0.31 μmol/L·s, respectively. The experiment of enzymatic reaction from L-DOPA to dopaquinone was conducted at 37°C with an enzyme concentration of 0.2 μg/mL. The calculated Michaelis constant (Km) and maximum velocity (Vmax) were 8787 μmol/L and 0.86 μmol/L·s, respectively.

Fig. 4 Tyrosinase TyrVs kinetic parameters

a-b.Michaelis-Menten plot and Lineweaver-Burk double reciprocal plot of enzymatic reaction from tyrosine to dopaquinone experiments. c-d.Michaelis-Menten plot and Lineweaver-Burk double reciprocal plot of enzymatic reaction from L-DOPA to dopaquinone experiments.

==== Reference ====
#TAN D, ZHAO J P, RAN G Q, et al. Highly efficient biocatalytic synthesis of L-DOPA using in situ immobilized Verrucomicrobium spinosum tyrosinase on polyhydroxyalkanoate nano-granules [J]. Appl. Microbiol. Biotechnol., 2019, 103(14): 5663-78.
#YAO L, WANG X, XUE R, et al. Comparative analysis of mussel foot protein 3B co-expressed with tyrosinases provides a potential adhesive biomaterial [J]. Int. J. Biol. Macromol., 2022, 195: 229-36. Sequence and Features BBa_K5398600 SequenceAndFeatures