Study of tyrosine and dopa enantiomers as tyrosinase substrates initiating L‐ and D‐melanogenesis pathways

Pedro Jesús Fernández Juliá, Jose Tudela‐Serrano, Francisco Garcia-Molina, Francisco Garcia-Canovas, Antonio García Jiménez, Jose Munoz*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
71 Downloads (Pure)

Abstract

Tyrosinase starts melanogenesis and determines its course, catalyzing the oxidation by molecular oxygen of tyrosine to dopa, and that of dopa to dopaquinone. Then, nonenzymatic coupling reactions lead to dopachrome, which evolves toward melanin. Recently, it has been reported that d-tyrosine acts as tyrosinase inhibitor and depigmenting agent. The action of tyrosinase on the enantiomers of tyrosine (l-tyrosine and d-tyrosine) and dopa (l-dopa and d-dopa) was studied for the first time focusing on quantitative transient phase kinetics. Post-steady-state transient phase studies revealed that l-dopachrome is formed more rapidly than d-dopachrome. This is due to the lower values of Michaelis constants for l-enantiomers than for d-enantiomers, although the maximum rates are equal for both enantiomers. A deeper analysis of the inter-steady-state transient phase of monophenols demonstrated that the enantiomer d-tyrosine causes a longer lag period and a lower steady-state rate, than l-tyrosine at the same concentration. Therefore, d-melanogenesis from d-tyrosine occurs more slowly than does l-melanogenesis from l-tyrosine, which suggests the apparent inhibition of melanin biosynthesis by d-tyrosine. As conclusion, d-tyrosine acts as a real substrate of tyrosinase, with low catalytic efficiency and, therefore, delays the formation of d-melanin.

Original languageEnglish
Pages (from-to)823-831
Number of pages9
JournalBiotechnology and Applied Biochemistry
Volume68
Issue number4
Early online date18 Aug 2020
DOIs
Publication statusPublished - 1 Aug 2021

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