Wheat Germ Agglutinin (WGA): Its Nature, Biological Role, Significance in Human Nutrition, and Possibility to Be Used as Marker of Whole-Grain Status in Wheat-Based Foods

Abstract

The growing scientific evidence on the health benefits of whole-grain food consumption has promoted the manufacturing of a great number of products differing in quality and content of whole-grain components. This is particularly true for commercial wheat-based products where it is not always clear how much whole wheat is present considering that in many cases, they are manufactured from reconstituted mill streams and that there is not a standardised globally accepted definition and metrics to objectively evaluate whole-grain status. Attempts have been made to assess the level of "wholegraininess" in wheat products by measuring specific constituents that correlate with different wheat tissues, especially those that are expected to be found in a true whole-grain wheat product. Wheat germ agglutinin (WGA), a small lectin protein present exclusively in the wheat-germ tissues, has been indicated by several scientists as one of these constituents and after founding that its level changes depending on the amount of germ found in a wheat flour, it has been indicated as a biomarker of whole-grain status for wheat products. In this review, the biochemistry of WGA, its methods of detection, and current knowledge on its possibility to be practically utilized as a reliable marker are critically discussed.

Keywords: ELISA; biomarker; lectins; wheat germ agglutinin; whole-grain food; wholegraininess.

Figure 1

Dimeric structure of the wheat germ agglutinin 3 (WGA isoform n.3) (in Balčiūnaitė-Murzienė et al., 2021 [29]). Red, orange, yellow, and brown colors represent the subunits A, B, C, and D of the first protein, respectively. Blue, light blue, pink, and purple represent the subunits A, B, C, and D of the second protein, respectively. The sugar-binding site is located at the interface of both WGA monomers.

Figure 2

Timeline of studies of WGA as marker of whole-grain status in wheat foodstuff [13,14,44,45,46,100,101,102,103,106,107].