Table 1.
Summary of the mutations to the six conserved histidines: effects on PPOs′ copper content and diphenolase/monophenolase activity. The modification of copper content and the activities′ rate are described compared to the wild type of the corresponding enzymes.
|
Conserved histidines | |||||
|---|---|---|---|---|---|
|
Enzyme |
Mutant |
Diphenolase activity |
Monophenolase activity |
Copper % |
Ref. |
|
CgAUS |
His93Ala (HisA1) |
−178‐fold (butein: 62 μmol/(l×min) −240‐fold (fisetin: 92 μmol/(l×min) −575‐fold (4‐tert‐butylcatechol: 218 μmol/(l×min) |
n.i. |
50 |
|
|
|
His116Ala‐(HisA2) |
n.d. (butein, fisetin, and 4‐tert‐butylcatechol) |
n.i. |
50 |
|
|
|
His125Ala‐(HisA3) |
n.d. (butein, fisetin, and 4‐tert‐butylcatechol) |
n.i. |
50 |
|
|
|
His252Ala‐(HisB1) |
n.d. (butein, fisetin, and 4‐tert‐butylcatechol) |
n.i. |
n.i. |
|
|
|
His256Ala‐(HisB2) |
−409‐fold (butein: 27 μmol/(l×min) n.d. (fisetin and 4‐tert‐butylcatechol) |
n.i. |
n.i. |
|
|
|
His286Ala‐(HisB3) |
n.d. (butein, fisetin, and 4‐tert‐butylcatechol) |
n.i. |
n.i. |
|
|
HsTYR |
His363Ala‐(HisB1) |
n.i. |
n.d. (l‐tyrosine) |
0 |
|
|
|
His367Ala‐(HisB2) |
n.i. |
n.d. (l‐tyrosine) |
50 |
|
|
|
His390Ala‐(HisB3) |
n.i. |
n.d. (l‐tyrosine) |
250 |
|
|
|
His180Ala‐(HisA1) |
−1.20‐fold (l‐DOPA: 28.5 s−1) |
−1.79‐fold (l‐tyrosine: 0.34 s−1) |
n.i. |
|
|
|
His202Ala‐(HisA2) |
−1.14‐fold (l‐DOPA: 30.0 s−1) |
−1.45‐fold (l‐tyrosine: 0.42 s−1) |
n.i. |
|
|
|
His211Ala‐(HisA3) |
−1.05‐fold (l‐DOPA: 32.4 s−1) |
−1.22‐fold (l‐tyrosine: 0.50 s−1) |
n.i. |
|
|
|
His363Ala‐(HisB1) |
−1.98‐fold (l‐DOPA: 17.2 s−1) |
−1.38‐fold (l‐tyrosine: 0.44 s−1) |
n.i. |
|
|
|
His367Ala‐(HisB2) |
−2.16‐fold (l‐DOPA: 15.8 s−1) |
−1.27‐fold (l‐tyrosine: 0.48 s−1) |
n.i. |
|
|
|
His390Ala‐(HisB3) |
−1.15‐fold (l‐DOPA: 29.7 s−1) |
−1.17‐fold (l‐tyrosine: 0.52 s−1) |
n.i. |
|
|
AoTYR[a] |
His63Asn‐(HisA1) |
n.d. (l‐DOPA) |
n.d. (l‐tyrosine) |
45 |
|
|
|
His84Asn‐(HisA2) |
n.d. (l‐DOPA) |
n.d. (l‐tyrosine) |
35 |
|
|
|
His93Asn‐(HisA3) |
n.d. (l‐DOPA) |
n.d. (l‐tyrosine) |
50 |
|
|
|
His290Asn‐(HisB1) |
n.d. (l‐DOPA) |
n.d. (l‐tyrosine) |
30 |
|
|
|
His294Asn‐(HisB2) |
n.d. (l‐DOPA) |
n.d. (l‐tyrosine) |
40 |
|
|
|
His333Asn‐(HisB3) |
n.d. (l‐DOPA) |
n.d. (l‐tyrosine) |
40 |
|
|
SgTYR |
His37Gln‐(HisA1) |
−12500‐fold (l‐DOPA: ∼0.2 units/mg) |
n.i. |
55 |
|
|
|
His53Gln‐(HisA2) |
−12500‐fold (l‐DOPA: ∼0.2 units/mg) |
n.i. |
45 |
|
|
|
His62Asn‐(HisA3) |
−12500‐fold (l‐DOPA: ∼0.2 units/mg) |
n.i. |
55 |
|
|
|
His189Asn‐(HisB1) |
−12500‐fold (l‐DOPA: ∼0.2 units/mg) |
n.i. |
90 |
|
|
|
His193Gln‐(HisB2) |
−6250‐fold (l‐DOPA: 0.4 units/mg) |
n.i. |
50 |
|
|
|
His215Gln‐(HisB3) |
−2778‐fold (l‐DOPA: 0.9 units/mg) |
n.i. |
85 |
|
|
ScTYR |
His63Phe‐(HisA3) |
n.i. |
n.d. (l‐tyrosine) |
n.i. |
|
[a] Refers to AoTYR (mel0‐Q00234). n.d.: no detected activity, n.i.: no information from the particular study, entries in μmol/(l×min) refer to volumetric activity, s‐1 to kcat values, and units/mg to specific enzymatic activity. One unit of enzymatic activity is defined as that amount of enzyme that catalyzes the formation of one μmol of product (ortho‐quinone) per minute under reaction conditions optimized for quickest conversion of the respective educt.