Suicide inactivation of tyrosinase in its action on tetrahydropterines

Tetrahydrobiopterin (BH4), methyl-tetrahydropterin (MBH4) and dimethyl-tetrahydropterin (DMBH 4) are oxidized by tyrosinase in a process during which the suicide inactivation of tyrosinase may occur. From the kinetic study of this process, lambda(SR)(Eox)((max)) (apparent maximum constant for the suicide inactivation), K-m(SR) (Michaelis constant for the substrate) and r (number of turnovers that the enzyme makes before the inactivation) can be obtained. From the results obtained, it can be deduced that the velocity of the inactivation governed by (lambda(SR)(Eox)((max))) and the potency of the same (lambda(SR)(Eox)((max))/K-m(SR)) follow the order: BH4 > MBH4 > DMBH4.