General Trend of Lipase to Self-Assemble Giving Bimolecular Aggregates Greatly Modifies the Enzyme Functionality

Abstract

Three microbial lipases (those from Candida rugosa, Humicola lanuginosa, and Mucor miehei) have been found to exhibit a tendency to form bimolecular aggregates in solution even at very low enzyme concentrations (44 microg/mL) in the absence of a detergent, as detected by gel filtration. The monomolecular form of the enzymes was found as unique only at low enzyme concentration and in the presence of detergents. However, in the case of the lipase B from Candida antarctica, no bimolecular form could be identified even at enzyme concentrations as high as 1.2 mg/mL in the absence of detergent. It has been stated that bimolecular and monomolecular structures display very different functional properties: (i) the enzyme specific activity decreased when the lipase concentration increased; (ii) the bimolecular form was much more stable than the monomeric one yielding a higher optimal T (increasing between 5 and 10 degrees C) and higher stability in inactivation experiments (the dimer half-life became several orders of magnitude higher than that of the monomer); (iii) the enantioselectivity depended on the enzyme concentration even after immobilization. For example, with use of the lipase from H. lanuginosa, the enantiomeric excess of the remaining ester in the hydrolysis of fully soluble ethyl ester of (R,S)-2-hydroxy-4-phenylbutanoic acid varied from 4 to 57 when the concentrated or diluted enzyme immobilized on PEI support, respectively, was used. It seems that the bimolecular structure of lipases might be formed by two open lipase molecules (interfacially activating each other) in very close contact and hence with a very altered active center.

Lipase biocatalytic processes in surfactant free microemulsion-like ternary systems and related organogels

“…It seems that, despite the structural similarities between the two lipases (similar molecular size and high degree of homology), in the case of CaL-B, such unfavorable protein-hydrophobic interface interactions were not dominant. This is in accordance to other studies concerning the catalytic and stability behavior of these lipases in various systems [22,23].…”

“…3). As it was discussed before, the lower stability of RmL could be attributed to unfavourable inter- actions of the enzyme molecules with the hydrophobic interface [22,23].…”

“…Lipases used in the present work are largely employed in biocatalysis and accept a broad range of substrates. Their catalytic and stability behavior in various reaction media has been reported to differ, depending on their ability to interact with interfaces, presenting (as in the case of RmL) or not (as in the case of CaL-B), the phenomenon of interfacial activation [21][22][23]. The aimed biotechnological application of such lipase-containing surfactant free systems was demonstrated through the examples of the esterification of both non-polar fatty acids and relatively polar compounds such as natural phenolic antioxidants including cinnamic acid derivatives.…”

Immobilization of enzymes on heterofunctional epoxy supports

“…However, by adding a small concentration of detergents (e.g., 0.5% Triton X-100), adsorption via interfacial activation may be fully prevented 29 , and lipases will become adsorbed by the groups inserted in the matrix. Other possible problems using lipases is their tendency to form lipase-lipase dimers with altered properties; this is also solved using detergents [50][51][52] .…”

Targeting Cancer with Bugs and Liposomes: Ready, Aim, Fire

“…In other lipases, this lid plays a key role by adopting an ''open-lid'' conformation upon contact with a water-lipid phase boundary to allow access of lipids to the catalytic center. One tantalizing possibility is that physical interaction between the open hydrophobic lid of one liposomase molecule and the exposed catalytic area of another open molecule might enable the self-assembly of liposomase molecules into multimeric structures able to disrupt lipid membranes (22). This remains a hypothesis to be tested.…”