2000
DOI: 10.1046/j.1432-1327.2000.01013.x
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Kinetic characterization of the substrate specificity and mechanism of mushroom tyrosinase

Abstract: This paper reports a quantitative study of the effect of ring substituents in the 1-position of the aromatic ring on the rate of monophenol hydroxylation and o-diphenol oxidation catalyzed by tyrosinase. A possible correlation between the electron density of the carbon atom supporting the oxygen from the monophenolic hydroxyl group and the V M max values for each monophenol was found. In the case of o-diphenols the same effect was observed but the size of the side-chain became very important. NMR studies on th… Show more

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Cited by 209 publications
(186 citation statements)
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“…Thus, in the case of NADH, the attack can be carried out by an oxygen atom of the nicotinamide ring, while in the case of 6BH 4 it is a nitrogen atom (a stronger nucleophile) that carries out the attack. As has been found for the case of monophenols and diphenols, 28) the values of k cat reflect the power of the nucleophilic attack. The Fig.…”
Section: Kinetic Characterization Of Tyr Action On Nadhsupporting
confidence: 52%
“…Thus, in the case of NADH, the attack can be carried out by an oxygen atom of the nicotinamide ring, while in the case of 6BH 4 it is a nitrogen atom (a stronger nucleophile) that carries out the attack. As has been found for the case of monophenols and diphenols, 28) the values of k cat reflect the power of the nucleophilic attack. The Fig.…”
Section: Kinetic Characterization Of Tyr Action On Nadhsupporting
confidence: 52%
“…To elucidate the type of inhibition exactly, we used two other linearization methods, namely, the Dicson and one-curve method plots ( Figure 5A and 5B). The set of curves on these plots completely satisfied the competitive type of inhibition 34 . The inhibition constant for PTU was estimated from each of the used linearization plots.…”
Section: Resultsmentioning
confidence: 65%
“…To determine the type of inhibition, the Lineweaver-Burk, the Hanes-Woolf, and the Eadie-Hofstee linearizations were used. In the case of competitive type of inhibition, the intersection points of the curves must be on the axes on the Lineweaver-Burk and the Eadie-Hofstee plots 34 . All used linearizations presented on Figure 4B, 4C, and 4D indicate that the type of inhibition of PO by PTU is competitive or complex with dominance of competitive type, as the intersection points slightly deviate from ordinate axes on the plots ( Figure 4B and 4D) that could indicate the complex type of inhibition.…”
Section: Resultsmentioning
confidence: 99%
“…These K m values compare favourably with those reported for tyramine (0.51 mM) and dopamine (2.2 mM). The V max values correspond to turnover numbers of 0.6 s-1 and 6 s-1 for 5c and 5f, respectively, which are rather smaller than the 25.9 s -1 and 439 s -1 observed for tyramine and dopamine substrates [18], though the relative sizes between the tyramine and dopamine derivatives are similar. This observation is consistent with the report that tyrosinase accepts mono-, di-and trihydroxyphenols as substrates but displays the highest turnover rates for dihydroxyphenols [19,20].…”
Section: Stability In Phosphate Buffer and Human Plasmamentioning
confidence: 65%