5'->3' DNA exonuclease which digests single-stranded DNA (ssDNA). Regulates inflammatory cytokine responses via the degradation of nucleic acids, by reducing the concentration of ssDNA able to stimulate TLR9, a nucleotide-sensing receptor. Involved in phagocytosis of activated microglia. Exonucleolytic cleavage in the 5'- to 3'-direction to yield nucleoside 3'-phosphates. Activation of microglia induces translocation of PLD4 from the nucleus to the phagosomes. Highly N-glycosylated. Belongs to the phospholipase D family. Exhibits no phospholipase activity, despite two HKD motifs.