 APOA1 encodes a 45.4 kDa protein that is composed of 396 amino acids; 21 peptides have been observed through mass spectrometry data.Apolipoprotein A1 is the major protein component of HDL particles in plasma.Chylomicrons secreted from the intestinal enterocyte also contain apo A1, but it is quickly transferred to HDL in the bloodstream.