A. Hickel et al., HYDROXYNITRILE LYASE ADSORPTION AT LIQUID LIQUID INTERFACES/, Journal of molecular catalysis. B, Enzymatic, 5(1-4), 1998, pp. 349-354
The adsorption behavior of hydroxynitrile lyase from Prunus amygdalus
(p-Hnl) at liquid/liquid interfaces has been investigated using dynami
c-interfacial-tension measurements. Unfolding of proteins at organic/a
queous interfaces results in a decrease of interfacial tension due to
an increasing number of interfacial contacts of hydrophobic parts of t
he protein molecule. Seven organic solvents with different physical pr
operties, including hexadecane, heptane, diisopropyl ether (DIPE) and
ethyl acetate, were studied. It is known that p-Hnl loses its activity
very quickly in a variety of solvents, but not in DIPE and ethyl acet
ate, For these two organic solvents, dynamic interfacial tensions rema
in constant over a period of 20 h. However, slow decline in the dynami
c interfacial tension is found for the less polar solvents suggesting
that the protein adsorbs and denatures. Additionally, experiments have
been carried out with the aqueous buffer phase at low pH values down
to 3.5 with DIPE as the organic phase, simulating conditions that have
been previously used for the synthesis of cyanohydrins. There, it is
known that the enzyme loses its activity very quickly. Correspondingly
, the interfacial tension decreases under these conditions indicating
that the bulk enzyme denatures and adsorbs at the interface in an unfo
lded configuration. (C) 1998 Elsevier Science B.V. All rights reserved
.