Journal
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
Volume 59, Issue 4, Pages 1383-1391Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jf1035433
Keywords
Tetrahydrofolic acid; tyrosinase; mechanism; suicide; inactivation
Funding
- Ministerio de Educacion y Ciencia (Madrid, Spain) [BIO2009-12956, CTQ2009-13023, SAF2009-12043-C02-01]
- Fundacion Seneca (CARM, Murcia, Spain) [08856/PI/08, 08813/PI/08, 08595/PI/08]
- Fundacion Caja Murcia (Murcia, Spain)
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The coenzyme tetrahydrofolic acid is the most rapid suicide substrate of tyrosinase that has been characterized to date. A kinetic study of the suicide inactivation process provides the kinetic constants that characterize it: lambda(max), the maximum apparent inactivation constant; r, the partition ratio or the number of turnovers made by one enzyme molecule before inactivation; and k(cat) and K-m, the catalytic and Michaelis constants, respectively. From these values, it is possible to establish the ratio lambda(max)/K-m, which represents the potency of the inactivation process. Besides acting as a suicide substrate of tyrosinase, tetrahydrofolic acid reduces o-quinOnes generated by the enzyme in its action on substrates, such as L-tyrosine and L-DOPA (o-dopaquinone), thus inhibiting enzymatic browning.
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