Energy Transfer Studies between Trp Residues of Three Lipocalin Proteins Family, α1-Acid Glycoprotein, (Orosomucoid), β-Lactoglobulin and Porcine Odorant Binding Protein and the Fluorescent Probe, 1-Aminoanthracene (1-AMA)

Biotechnological applications of mammalian odorant-binding proteins

The olfactory system of mammals allows the detection and discrimination of thousands of odors from the environment. In mammals, odorant-binding proteins (OBPs) are considered responsible to carry odorant molecules across the aqueous nasal mucus to the olfactory receptors (ORs). The three-dimensional structure of these proteins presents eight antiparallel β-sheets and a short α-helical segment close to the C terminus, typical of the lipocalins family. The great ability of OBPs to bind differentiated ligand molecules has driven the research to understand the mechanisms underlying the OBP function in nature and the development of advanced biotechnological applications. This review describes the role of mammalian OBPs in the olfactory perception, highlighting the influence of several key parameters (amino acids, temperature, ionic strength, and pH) in the formation of the OBP/ligand complex. The information from the literature regarding OBP structure, affinity, the strength of binding, and stability inspiring the development of several applications herein detailed.

Changes in structure and antioxidant activity of β-lactoglobulin by ultrasound and enzymatic treatment

Effects of ultrasound (20-40% amplitudes at 45-55 °C) and enzymatic (pepsin and trypsin) treatment on structure and antioxidant activity of β-lactoglobulin were studied. Changes in structure of β-lactoglobulin were investigated using spectroscopy techniques and changes in antioxidant activity were measured by chemical and cellular-based assays. Ultrasound treatment had considerable impact on the structure of β-lactoglobulin and increased the susceptibility of β-lactoglobulin to both pepsin and trypsin proteolysis. Intrinsic fluorescence intensity of β-lactoglobulin was increased by ultrasound and then decreased after following enzymatic treatment. Compared with control, the β-lactoglobulin after ultrasound and enzymatic treatments showed significantly higher oxygen scavenging activities in Caco-2 cells models, ABTS (2, 2'-Azinobis-3-ethylbenzthiazoline-6-sulphonate) radical scavenging activity and oxygen radical absorbance capacity (p < 0.05). Results indicated that ultrasound treatment increased the proteolysis of β-lactoglobulin by both pepsin and trypsin and improved the antioxidant activity of the protein and its proteolytic products.