Role of lysine epsilon-amino groups of beta-lactoglobulin on its activating effect of Kluyveromyces lactis beta-galactosidase.
Native beta-lactoglobulin binds and increases the activity of Kluyveromyces lactis beta-galactosidase. Construction of a three-dimensional (3D) model of beta-lactoglobulin showed that lysine residues 15, 47, 69, and 138 are the most exposed ones, thus the ones more likely to interact with beta-galactosidase. Molecular docking estimated the interaction energies of amino acid residues with either lactose or succinic anhydride, showing that Lys(138) is the most likely to react with both. Affinity chromatography demonstrated that succinylated beta-lactoglobulin diminished its ability to bind to the enzyme. Furthermore, when activity was measured in the presence of succinylated beta-lactoglobulin, its activating effect was lost. Since succinylation specifically blocks Lys epsilon-amino groups, their loss very likely causes the disappearance of the activating effect. Results show that the activating effect of beta-lactoglobulin on beta-galactosidase activity is due to the interaction between both proteins and that this interaction is very likely to occur through the Lys epsilon-amino groups of beta-lactoglobulin.
Del Moral-Ramírez
Elizabeth
E
Departamento de Biotecnologia, Universidad Autonoma Metropolitana, Iztapalapa, Mexico City, Mexico.
Domínguez-Ramírez
Lenin
L
Cruz-Guerrero
Alma E
AE
Rodríguez-Serrano
Gabriela M
GM
García-Garibay
Mariano
M
Gómez-Ruiz
Lorena
L
Jiménez-Guzmán
Judith
J
D001665:Binding Sites; D004789:Enzyme Activation / Q000187:drug effects*; D007716:Kluyveromyces / Q000201:enzymology*; D007782:Lactoglobulins / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D008239:Lysine / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D013816:Thermodynamics; D001616:beta-Galactosidase / Q000378:metabolism*
D007782:Lactoglobulins; D001616:beta-Galactosidase; D008239:Lysine