[14] The protein is an aspartyl protease that functions as a disulfide-linked homodimer, and has an oligosaccharide chain of the high-mannose type.

It is found at highest abundance on the stomach’s epithelial mucus producing cell surfaces.

It is the first aspartic protease present in the fetal stomach and is found in more than half of gastric cancers, leading to it appearing to be an oncofetal antigen.

Two other Cys residues at positions 109 and 114 on the amino acid chain reside close to teach other in three dimensional space, however the distance between their sulfur atoms is 3.53 Å which is too large for the formation of a proper disulfide bond.

The enzyme is also thought to be involved in age induced neuronal death pathway execution as well as the excessive stimulation of glutamate receptors with excitotoxins and transient forebrain ischemia.

The enzyme was also expressed at high levels in the activated microglia of the hippocampal CA1 region and in degenerating neurons for a week after transient forebrain ischemia.

[15] The enzyme also plays a part in association with dendritic cells where it generates the CD4 repertoire in response to self and foreign proteins.