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N-Acetyl-L-Tyrosine (NAT) as a Substrate for Mushroom Tyrosinase
Year:
1998
Source of publication :
Pigment Cell Research
Authors :
Ben-Shalom, Noach
;
.
Kahn, Varda
;
.
Volume :
11
Co-Authors:
Kahn, V., Department of Food Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel, Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Ben-Shalom, N., Department of Food Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Facilitators :
From page:
24
To page:
33
(
Total pages:
10
)
Abstract:
N-acetyl tyrosine (NAT) is hydroxylated by mushroom tyrosinase and the N-acetyl dopa formed is oxidized by the enzyme to N-acetyl dopaquinone (λmax = 390 ± 10 nm). H2O2 and NH2OH each shortened the lag period of NAT hydroxylation by the enzyme. H2O2 had an effect on the changes with time in the spectrum of product(s) formed and on the spectrum of the final product(s) obtained when NAT was hydroxylated by mushroom tyrosinase, in a manner suggesting that H2O2 converts N-acetyl dopaquinone to a pink-violet product(s) (λmax = 490 nm), whereas such a product(s) was not formed in the absence of H2O2. A pink-violet product(s) (λmax 490 ± 20 nm) was also formed when NAT was hydroxylated by mushroom tyrosinase in the presence of NH2OH or para amino benzoic acid (PABA), probably as a result of an interaction between N-acetyl dopaquinone and NH2OH or PABA forming mono- or di-oximes. Kojic acid (5-hydroxy-2-hydroxymethyl)-4H-pyran-4-one) inhibited effectively the rate of NAT hydroxylation by mushroom tyrosinase in the absence or presence of H2O2. When NAT was oxidized by the enzyme in the absence of kojic acid, N-acetyl dopaquinone was formed at once and a shoulder at 490-530 nm appeared later. Under identical conditions but in the presence of kojic acid, a yellow product(s), characterized by a peak at 320±10 nm, was detected, suggesting that N-acetyl dopaquinone oxidizes kojic acid to the yellow product(s). Maltol (3-hydroxy-2-methyl-4H-pyran-4-one), a γ-pyrone derivative structurally related to kojic acid, also inhibited the rate of NAT hydroxylation by mushroom tyrosinase. The addition of maltol at the plateau phase of the reaction resulted in an immediate decline in absorbance at 400 nm, suggesting that maltol conjugates with N-acetyl dopaquinone, yielding a product(s) characterized by a lower extinction coefficient at 400 nm than that of N-acetyl dopaquinone alone. The final brown-red product(s) formed when NAT was hydroxylated by mushroom tyrosinase was bleached in the presence of ascorbic acid or H2O2.
Note:
Related Files :
Basidiomycota
chemistry
drug derivative
drug effect
kojic acid
metabolism
n acetyltyrosine
tyrosine
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More details
DOI :
Article number:
Affiliations:
Database:
Scopus
Publication Type:
article
;
.
Language:
English
Editors' remarks:
ID:
32520
Last updated date:
02/03/2022 17:27
Creation date:
17/04/2018 01:10
Scientific Publication
N-Acetyl-L-Tyrosine (NAT) as a Substrate for Mushroom Tyrosinase
11
Kahn, V., Department of Food Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel, Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Ben-Shalom, N., Department of Food Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
N-Acetyl-L-Tyrosine (NAT) as a Substrate for Mushroom Tyrosinase
N-acetyl tyrosine (NAT) is hydroxylated by mushroom tyrosinase and the N-acetyl dopa formed is oxidized by the enzyme to N-acetyl dopaquinone (λmax = 390 ± 10 nm). H2O2 and NH2OH each shortened the lag period of NAT hydroxylation by the enzyme. H2O2 had an effect on the changes with time in the spectrum of product(s) formed and on the spectrum of the final product(s) obtained when NAT was hydroxylated by mushroom tyrosinase, in a manner suggesting that H2O2 converts N-acetyl dopaquinone to a pink-violet product(s) (λmax = 490 nm), whereas such a product(s) was not formed in the absence of H2O2. A pink-violet product(s) (λmax 490 ± 20 nm) was also formed when NAT was hydroxylated by mushroom tyrosinase in the presence of NH2OH or para amino benzoic acid (PABA), probably as a result of an interaction between N-acetyl dopaquinone and NH2OH or PABA forming mono- or di-oximes. Kojic acid (5-hydroxy-2-hydroxymethyl)-4H-pyran-4-one) inhibited effectively the rate of NAT hydroxylation by mushroom tyrosinase in the absence or presence of H2O2. When NAT was oxidized by the enzyme in the absence of kojic acid, N-acetyl dopaquinone was formed at once and a shoulder at 490-530 nm appeared later. Under identical conditions but in the presence of kojic acid, a yellow product(s), characterized by a peak at 320±10 nm, was detected, suggesting that N-acetyl dopaquinone oxidizes kojic acid to the yellow product(s). Maltol (3-hydroxy-2-methyl-4H-pyran-4-one), a γ-pyrone derivative structurally related to kojic acid, also inhibited the rate of NAT hydroxylation by mushroom tyrosinase. The addition of maltol at the plateau phase of the reaction resulted in an immediate decline in absorbance at 400 nm, suggesting that maltol conjugates with N-acetyl dopaquinone, yielding a product(s) characterized by a lower extinction coefficient at 400 nm than that of N-acetyl dopaquinone alone. The final brown-red product(s) formed when NAT was hydroxylated by mushroom tyrosinase was bleached in the presence of ascorbic acid or H2O2.
Scientific Publication
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