About PGA4
This gene encodes a protein precursor of the digestive enzyme pepsin, a member of the peptidase A1 family of endopeptidases. The encoded precursor is secreted by gastric chief cells and undergoes autocatalytic cleavage in acidic conditions to form the active enzyme, which functions in the digestion of dietary proteins. This gene is found in a cluster of related genes on chromosome 11, each of which encodes one of multiple pepsinogens. Pepsinogen levels in serum may serve as a biomarker for atrophic gastritis and gastric cancer. [provided by RefSeq, Jul 2015]

About APC
Allophycocyanin (APC) is a fluorescent protein derived from cyanobacteria and red algae and a potent donor fluorophore to create tandem dyes that can be excited off the 633-640 nm laser. APC has an excitation peak at 650 nm and a emission peak at 660 nm.