Korištenje Lewisovih stanica u istraživanju enzimske kinetike (S)-hidroksinitril liaze u dvofaznom sustavu

(S)-Hydroxynitrile lyase from Hevea brasiliensis (HbHnl) (EC 4.1.2.39) catalyzes the reversible synthesis of chiral cyanohydrins from aldehydes or ketones and HCN. The enzymatic formation of (S)-mandelonitrile (MN) from benzaldehyde (BA) and HCN was studied in two-phase systems of buffer and organic solvents (diisopropyl ether, methyl-t-butyl ether) using a Lewis cell to investigate the interaction between mass transfer and the biocatalytic reaction. The enzymatic reaction rate in the aqueous phase saturated with organic solvents is drastically reduced in comparison to pure buffer due to the increase of the Michaelis-Menten constants of the substrates. Mass transfer of the substrates from the organic to the aqueous phase and mass transfer of the product in the opposite direction could be described by the two-film theory. The formation of (S)-mandelonitrile in the Lewis cell follows an aqueous phase distributed reaction model, which means that the enzymatic reaction takes place in the bulk of the aqueous phase and in the thin film close to the interface and/or directly at the interface. Using the Hatta number it could be shown that the mass transfer of benzaldehyde from the organic to the aqueous phase is enhanced by the biocatalytic reaction of the (S)-hydroxynitrile lyase from Hevea brasiliensis.(S)-hidroksinitril liaza iz Hevea brasiliensis (HbHnl) (EC 4.1.2.39) katalizira reverzibilnu sintezu kiralnih cianohidrina iz aldehida ili ketona i HCN. Enzimska sinteza (S)-mandelonitrila (MN) iz benzaldehida (BA) i HCN ispitivana je u dvofaznim sustavima pufera i organskih otapala (diizopropileter, metil-t-butileter) koristeći Lewisovu stanicu kako bi se istražilo međudjelovanje prijenosa mase i biokatalitičke reakcije. Brzina enzimske reakcije u vodenoj fazi, zasićenoj organskim otapalima, drastično je smanjena u usporedbi s reakcijom u čistom puferu zbog povišenja Michaelis-Mentenove š konstante supstrata. Prijenos mase supstrata iz organske u vodenu fazu te prijenos mase produkta u suprotnom smjeru može se opisati teorijom dvostrukog filma. Stvaranje (S)-mandelonitrila u Lewisovoj stanici slijedi reakcijski model u vodenoj fazi, što znači da se enzimska reakcija provodi uglavnom u vodenoj fazi i u tankom filmu u blizini međufaze odnosno izravno na međufazi. Koristeći Hattin broj moglo se pokazati da je prijenos mase benzaldehida iz organske u vodenu fazu pojačan biokatalitičkom reakcijom (S)-hidroksinitril liaze iz Hevea brasiliensis

Hydroxynitrile Lyases: Biological Sources and Application as Biocatalysts

We review the state of the art regarding the application of hydroxynitrile lyases to obtain, enantioselectively, (R)- and (S)-cyanohydrins of aldehydes and ketones. Special emphasis is given to recent preparative applications and to research for extending the number of plants serving as sources for the enzyme. Depending on the plant family, the mechanism of the enzyme-catalysed reaction can be different. A novel area of research is the consideration of evolutionary aspects on the basis of structure comparisons

The Use of Lewis Cell to Investigate the Enzyme Kinetics of an (S)-Hydroxynitrile Lyase in Two-Phase Systems

(S)-Hydroxynitrile lyase from Hevea brasiliensis (HbHnl) (EC 4.1.2.39) catalyzes the reversible synthesis of chiral cyanohydrins from aldehydes or ketones and HCN. The enzymatic formation of (S)-mandelonitrile (MN) from benzaldehyde (BA) and HCN was studied in two-phase systems of buffer and organic solvents (diisopropyl ether, methyl-t-butyl ether) using a Lewis cell to investigate the interaction between mass transfer and the biocatalytic reaction. The enzymatic reaction rate in the aqueous phase saturated with organic solvents is drastically reduced in comparison to pure buffer due to the increase of the Michaelis-Menten constants of the substrates. Mass transfer of the substrates from the organic to the aqueous phase and mass transfer of the product in the opposite direction could be described by the two-film theory. The formation of (S)-mandelonitrile in the Lewis cell follows an aqueous phase distributed reaction model, which means that the enzymatic reaction takes place in the bulk of the aqueous phase and in the thin film close to the interface and/or directly at the interface. Using the Hatta number it could be shown that the mass transfer of benzaldehyde from the organic to the aqueous phase is enhanced by the biocatalytic reaction of the (S)-hydroxynitrile lyase from Hevea brasiliensis