Peanut agglutinin (PNA) is plant lectin protein derived from the fruits of Arachis hypogaea.

The name "peanut agglutinin" originates from its ability to stick together (agglutinate) cells, such as neuraminidase-treated erythrocytes,[1] which have glycoproteins or glycolipids on their surface which include the Gal-β(1-3)-GalNAc carbohydrate sequence.

The protein is 273 amino acids in length with the first 23 residues acting as a signal peptide which is subsequently cleaved.

For example in PNA-affinity chromatography the binding specificity of peanut agglutinin is used to isolate glycosylated molecules which have the sugar sequence Gal-β(1-3)-GalNAc.

Peanut agglutinin activity is inhibited by lactose and galactose which compete for the binding site.