Its main function is inhibition of cholesteryl ester transfer protein (CETP), probably by altering the electric charge of HDL molecules.

When proteins rich in triglycerides like chylomicrons and VLDL are broken down, this apoprotein is transferred again to HDL.

Old World monkeys and great apes other than humans have been shown to have two active genes.

One of the duplicates encodes a basic protein designated apoC-IB that is orthologous to human apolipoprotein C-I.

The pseudogenization event occurred sometime between the divergence of bonobos and chimpanzees from the human lineage and the arrival of Denisovans and Neandertals.