Species: Phlebodium aureum
Subunit composition of (R)-mandelonitrile lyase = [(R)-mandelonitrile lyase subunit]8
The enzymatic accelerated cleavage of (R)-mandelonitrile into benzaldehyde and hydrogen cyanide is been catalyzed by mandelonitrile lyases. The (R)-mandelonitrile lyase purified from fronds of Phlebodium aureum is a multimer of 20 kDa and is involved in the bioactivation of R-vicianin as this is the only cyanogenic glucoside found in the fern. In contrast to the counterpart enzyme in Rosacea utilizing the same substrate, i.e. (R)-mandelonitrile the fern (R)-mandelonitrile lyase contains no flavin prosthetic group and shares no common properties with the rose (R)-mandelonitrile lyase.
Inhibitor studies indicated that the (R)-mandelonitrile lyase of Phlebodium aureum may operate a different catalytic mechanism compared to other mandelonitrile lyases. The amino acids cysteine and serine are seemingly not involved in catalysis but histidine is. At least three isoenzymes exist in Phlebodium aureum which all are consistent regarding structure and catalytic activities.
When immobilized in organic solvents the (R)-mandelonitrile lyase of Phlebodium aureum also catalyzes the addition of cyanide to aromatic and heterocyclic carbonyls indicating its usefulness for engineered pathways [Wajant95].
Molecular Weight of Polypeptide: 20.0 kD (experimental) [Wajant95]
Molecular Weight of Multimer: 168.0 kD (experimental) [Wajant95]
Enzymatic reaction of: (R)-mandelonitrile lyase
EC Number: 18.104.22.168(R)-mandelonitrile → hydrogen cyanide + benzaldehyde
The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction in which it was curated.
The reaction is physiologically favored in the direction shown.
In Pathways: vicianin bioactivationInhibitors (Unknown Mechanism): diethylpyrocarbonate [Wajant95]Kinetic Parameters:
|Substrate||Km (μM)||Vmax (µmol mg-1 min-1)||Citations|
T(opt): 25-40 °C [Wajant95]
pH(opt): 6.5 [Wajant95]
Wajant95: Wajant H, Forster S, Selmar D, Effenberger F, Pfizenmaier K (1995). "Purification and Characterization of a Novel (R)-Mandelonitrile Lyase from the Fern Phlebodium aureum." Plant Physiol 109(4);1231-1238. PMID: 12228664
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