Ultrasonic Pretreatment Combined with Dry-State Glycation Reduced the Immunoglobulin E/Immunoglobulin G-Binding Ability of α-Lactalbumin Revealed by High-Resolution Mass Spectrometry

Abstract

Bovine α-lactalbumin (α-LA) is one of major food allergens in cow's milk. The present work sought to research the effects of ultrasonic pretreatment combined with dry heating-induced glycation between α-LA and galactose on the immunoglobulin E (IgE)/immunoglobulin G (IgG)-binding ability and glycation extent of α-LA, determined by inhibition enzyme-linked immunosorbent assay and high-resolution mass spectrometry, respectively. The IgE/IgG-binding ability of glycated α-LA was significantly decreased as a result of ultrasonic pretreatment, while the average molecular weight, incorporation ratio (IR) value, location and number of glycation sites, and degree of substitution per peptide (DSP) value were elevated. When the mixtures of α-LA and galactose were pretreated by ultrasonication at 150 W/cm, glycated α-LA possesses seven glycation sites, the highest IR and DSP values, and the lowest IgE/IgG-binding ability. Therefore, the decrease in the IgE/IgG-binding ability of α-LA depends upon not only the shielding effect of the linear epitope found to be caused by the glycation of K13, K16, K58, K93, and K98 sites but also the intensified glycation extent, which reflected in the increase of the IR value, the number of glycation sites, and the DSP value. Moreover, allergenic proteins and monosaccharides pretreated by ultrasonication and then followed by dry-state glycation were revealed as a promising way of achieving lower allergenicity of proteins in food processing.

The IgE/IgG binding capacity and structural changes of Alaska Pollock parvalbumin glycated with different reducing sugars

“…The electrophilic activity of aldose is higher than that of ketose, and the terminal group has smaller steric hindrance, which makes the amino compounds are easier to approach (Jing & Kitts, 2004). The similar conclusion was drawn in our previous study on the α‐lactalbumin ultrasonic pretreatment combined dry‐state glycation (Liu, Tu, Liu, et al, 2018). As expected, the modification degree was direct relation between the sugar size and structure, they were PV‐Rib, PV‐Gal, PV‐Glu, PV‐Fru, and PV‐Lac, respectively.…”

Improved antitumor activity and IgE/IgG–binding ability of α‐Lactalbumin/β‐lactoglobulin induced by ultrasonication prior to binding with oleic acid

“…The milk protein‐specific IgE levels of five human antisera were 6.71, 9.977, 17.1, 43.6 and ≥100 kUA/L, respectively. Rabbit antisera were prepared by a previously reported protocol (Liu, Tu, Liu, et al., 2018).…”

“…The IgE/IgG–binding ability of α‐La, β‐Lg, N‐La‐OA, N‐Lg‐OA, U‐La‐OA, and U‐Lg‐OA was estimated by ELISA (Liu, Tu, Liu, et al., 2018). Human antisera (prepared by mixing the sera of five patients at the same volume) and rabbit antisera were applied to study the IgE/IgG–binding ability.…”

Observation of the structural changes of α‐lactalbumin induced by ultrasonic prior to glycated modification

“…For this study, K79 and K93 were identified in the glycated BLA after ultrasound pretreatment (Figure b). Our earlier study shows that glycated BLA mainly occurred on Lys (Liu, Tu, Liu, et al, ). It is of interest to point out that glycated site and DSP values could be altered by conformational structure of modified BLA via ultrasound.…”

“…Bovine α‐lactalbumin (BLA), one of the model Ca 2+ binding proteins that carries out diverse functions in the food and biology, as an ingredient of the function and nutrition (Liu, Tu, Shao, et al, ) and an ingredient for infant nutrition in the food. The BLA possesses a broad range of the functional properties, such as antioxidant (Liu, Tu, Shao, et al, ), immune‐modulating (Liu, Tu, Liu, et al, ), antibacterial (Sedaghati, Ezzatpanah, Boojar, & Ebrahimi, ), or antitumor activity (Fang, Zhang, Wu, Fan, & Ren, ), and so on. Chemical and physical methods are most popular modified technology capable of improving the structural and functional properties of protein (Liu, Tu, Yang et al, ; Yang, Tu, Wang, Li, & Tian, ).…”