The ‘HKD’ motifs, which define the catalytic core of the PLD enzymes, from human PLD1 and PLD2 (which contain two HKD motifs) and PLD6 (which contains one motif) are aligned with those from the FAM83 members using the Clustal Omega and BoxShade server. The first histidine (H) residue as well as identical residues conserved in more than 50% of the sequences are boxed in black and similar residues are boxed in grey. The positions of the HKD residues within the motifs are indicated by asterisks. All FAM83 proteins, except FAM83D, lack the first histidine and are therefore termed pseudo-PLDs.