Primate-specific plasma protein associated with apolipoprotein L-I (apoL-I)-containing high-density lipoprotein (HDL). This HDL particle, termed trypanosome lytic factor-1 (TLF-1), mediates human innate immune protection against many species of African trypanosomes. Binds hemoglobin with high affinity and may contribute to the clearance of cell-free hemoglobin to allow hepatic recycling of heme iron. Secreted into blood plasma and associated with subtypes of high density lipoproteins (HDL). In adult liver the amount of HPR mRNA is at the lower limit of detection, therefore the extent of its expression is at most less than 1000-fold that of the HP1F gene. No HPR mRNA can be detected in fetal liver. Expressed in Hep-G2 and leukemia MOLT-4 cell lines. The uncleaved signal sequence interacts with HDL fluid lipids and mediates incorporation into the HDL particle. Belongs to the peptidase S1 family. Although homologous to serine proteases, it has lost all essential catalytic residues and has no enzymatic activity.