Species: Secale cereale
The biosynthesis of luteolin 7-O-[β-D-glucosyluronate-(1,2)-β-D-glucosiduronate]-4'-O-β-D-glucosiduronate is carried out by three position specific flavone glucuronosyltransferases namely luteolin 7-O-glucuronosyltransferase (LGT), luteolin 7-O-glucuronide-glucuronosyltransferase (LMT) and luteolin 7-O-diglucuronide-glucuronosyltransferase (LDT). Enzymatic assays using partially purified enzymes from Secale cereale (rye) primary leaves revealed that they are not only position specific but also substrate specific. Further these enzymes did not show significant activity towards UDP-glucose, UDP-galactose, or UDP-xylose as sugar donors. The luteolin 7-O-diglucuronide-glucuronosyltransferase (LDT) was shown to catalyze the glucuronidation of luteolin 7-O-β-D-diglucuronide to form luteolin 7-O-[β-D-glucosyluronate-(1,2)-β-D-glucosiduronate]-4'-O-β-D-glucosiduronate [Schulz88]. Using cellular fractionation LMT could be localized to the vacuole [Anhalt92].
Locations: vacuolar lumen
Molecular Weight of Polypeptide: 29.0 kD (experimental) [Schulz88]
pI: 4.75 [Schulz88]
Enzymatic reaction of: luteolin-7-O-diglucuronide 4'-O-glucuronosyltransferase
EC Number: 18.104.22.168UDP-α-D-glucuronate + luteolin 7-O-β-D-diglucuronide → UDP + luteolin 7-O-[β-D-glucosyluronate-(1,2)-β-D-glucosiduronate]-4'-O-β-D-glucosiduronate + H+
The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the Enzyme Commission system.
The reaction is favored in the direction shown.
In Pathways: luteolin triglucuronide biosynthesisInhibitors (Uncompetitive): UDP [Schulz88] Inhibitors (Unknown Mechanism): luteolin [Schulz88]
|Substrate||Km (μM)||Vmax (µmol mg-1 min-1)||Citations|
T(opt): 40 °C [Schulz88]
pH(opt): 7 [Schulz88]
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