New assays for the tyrosine hydroxylase and dopa oxidase activities of tyrosinase
1991; Wiley; Volume: 198; Issue: 2 Linguagem: Inglês
10.1111/j.1432-1033.1991.tb16018.x
ISSN1432-1033
AutoresAlison J. Winder, Henry Harris,
Tópico(s)Advanced Glycation End Products research
ResumoNew assays for the tyrosine hydroxylase and dopa oxidase activities of tyrosinase (EC 1.14.18.1) have been developed. The tyrosine hydroxylase assay uses L ‐[ carboxy ‐ 14 C]tyrosine as the substrate. 14 CO 2 is released from the products of the hydroxylation and further metabolism of L ‐[ carboxy ‐ 14 C]tyrosine by incubation with ferricyanide, and measured radiometrically. D ‐Dopa is a preferable cofactor to L ‐dopa for the assay. Dopa oxidase activity is measured spectrophotometrically. Dopaquinone, produced on the oxidation of L ‐dopa, reacts with Besthorn's hydrazone (3‐methyl‐2‐benzothiazolinone hydrazone) to form a pink pigment with an absorbance maximum at 505 nm. Details of the optimisation of conditions for the assays and their specificities for the two enzyme activities are described.
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