Proline rich polypeptide (prp-1) increases the superoxide-producing and ferrihemoglobin reducing activities of cytochrome b₅₅₈ isoforms from human lymphosarcoma tissue cells

The two cytochromes (cyt) b₅₅₈ of acidic nature, one-95-100 kDa and another one, 60-70 kDa were isolated for the first time from the human's lymphosarcoma tissue cells using gel filtration and ion exchange chromatography. These hemoproteins possess NADPH dependent O₂ ^--producing and ferrihemoglobin-reducing activities. The incubation of neuropeptide PRP-1 (5 μg) with cytochrome b₅₅₈, caused elevation of these activities. The gel filtration results indicated possible binding of PRP-1 to these cytochromes b₅₅₈. PRP-1 activated both NADPH dependent O₂ ^--producing and ferriHb-reducing activities of the cyt b¹ ₅₅₈ and cyt b² ₅₅₈, obtained from human lymphosarcoma tissue cells. One can assume that PRP-1 associated with cyt b ₅₅₈ on the surface of the tumor cells by increasing both NADPH dependent O₂ ^--producing and ferriHb-reducing activities of cyt b₅₅₈, increases the oxidation- reduction status. Changing the oxidation-reduction status and oxygen homeostasis of the tumor cells by PRP-1 can serve as one of the possible explanation of antitumorigenic effect of this cytokine.