N-Acetyl-D-lactosamine is a disaccharide, consisting of galactose and N-acetylglucose units, which often appears as a structural element in glycoconjugates of biological significance, for example, it is a core unit of carbohydrates isolated from human milk.
Lectins are sugar-binding proteins with high specificity for their sugar moieties, and are typically involved in biological recognition processes involving cells and proteins. N-Acetyl-D-lactosamine and derivatives are widely used in the characterisation and investigation of the roles and utility of lectins from diverse sources.
For example, lectins from Arisaema intermedium, A. wallichianum, A. flavum
and A. helleborifolium
have specificity for N-Acetyl-D-lactosamine. In the case of A. helleborifolium
lectin (AHL), it has been shown that this has an in vitro anti-proliferative effect on several tumour cell lines, perhaps due to the ability to recognise carbohydrate profiles containing N-acetyl-D-lactosamine components on these cell lines. Additionally, in the same study, AHL was shown to have anti-insect activity.
N-Acetyl-D-lactosamine is an essential component of the tetrasaccharide Sialyl LewisX
, Figure 1, (also known as known as Sialyl LeX
), which is located on the terminus of glycolipids on the surface of leukocytes (white blood cells) such as neutrophils. Sialyl LewisX
plays an important role in inflammatory processes, mediating the adhesion of leukocytes to sites of injury via recognition of the lectin by E-selectin, an adhesion molecule on endothelial cells. High expression of Sialyl LewisX
has been observed in certain tumour cells, such as those in breast and colorectal cancer.
In addition to the role in the study of lectin inhibition, N-acetyl-D-lactosamine is also used in research into the roles of galactosidase, fucosyltransferase and sialyltransferase enzymes.
The wide spectrum of biological processes that N-acetyl-D-lactosamine and derivatives, and lectins recognizing this disaccharide, are involved in, coupled with their structural complexity, have made these materials and their analogues an intense area of synthetic research.
For example, Kretzschmar and Stahl have reported the synthesis of gram quantities of N-acetyl-D-lactosamine with a 1β-O-(6-amino)hexyl linker for evaluation and further derivitization towards the creation of antagonists of selectins for anti-inflammatory benefit, and Mong and colleagues have synthesized derivatives as part of a study of Sialyl LewisX
expression in a human monocytic cell line. An enzymatic synthesis of N-Acetyl-D-lactosamine using transformed yeast cells expressing a galactosyltransferase enzyme has been reported.
N-Acetyl-D-lactosamine is also known by multiple other names, including: LacNAc, β-D-Gal-(1→4)-D-GlcNAc, N-Acetyl-4-O-(β-D-galactopyranosyl)-D-glucosamine, beta-D-galactosyl-1,4-N-acetyl-D-glucosamine and 2-Acetamido-2-deoxy-4-O-β-D-galactopyranosyl-D-glucopyranose.