Pure and Applied Chemistry

Murine myelomonocytes WEHI-3 and human erythroid leukemia K562 cells were shown to release peptides into the surrounding medium. Four N-terminal sequences of the peptides derived from unknown protein precursors were identified in the conditioned medium of WEHI-3 culture. Twelve N-terminal sequences of the peptides released by K562 cells were established. K562 cells were shown to release long hemoglobin α- and ε-chains fragments, as well as peptides derived from carbonic anhydrase XI, melanophilin, cadherin EGF LAG G-type receptor 2, aldolase A, melastatin 1, peptide homologous to ryanodine receptor fragment, and a few peptides derived from the proteins with unknown function.

Comparative analysis of the peptides released by the intact erythroid leukemia K562 cells and the same cells after differentiation (induced by guanosine monophosphate, GMP, and accompanied by start of hemoglobin biosynthesis), has demonstrated that the level of six components, including all established hemoglobin fragments, carbonic anhydrase fragment, and the fragment of the unknown protein significantly increased in the course of differentiation. The spectrum of the peptides released by K562 cells strongly differed from that of the mature erythrocytes: (1) in contrast to the mature erythrocytes, K562 cells release long α-globin fragments and the fragment of ε-globin; (2) erythrocytes almost exclusively release the products of hemoglobin proteolysis; in the case of K562 cells the fragments of enzymes, receptors, and other functional proteins were found. So, the concentration and the content of the individual peptides released by the cells depend on the differentiation state.

The comparative analysis of the dynamics of peptide secretion by human erythrocytes performed in the presence and the absence of the 3 % glucose has shown that the rate of the peptide release strongly depends on cell metabolism. In summary, peptidomic studies of cell cultures provide valuable information on the mechanisms of peptide pool formation in tissues and the whole organism.