The antimalarial drugs chloroquine and primaquine inhibit pyridoxal kinase, an essential enzyme for vitamin B6 production.

•Quinoline derivatives, chloroquine and primaquine are used as antimalarial drugs.•Human pyridoxal kinase was identified as a binding protein of primaquine.•Primaquine inhibited pyridoxal kinases of malaria, trypanosome and human.•Chloroquine inhibited malaria pyridoxal kinase, but not human and trypanosome ones.•Pyridoxal kinase could be a target of antimalarial and adverse effects of the drugs.