The mean rate of trimming of N-terminal tryptophan (mol, substrate/mol, enzyme/sec) from 10-mer peptide WRVYEKCALK by wild-type ERAP1 and variants associated with ankylosing spondylitis (rs30187 (p.Lys528Arg), rs17482078 (p.Arg725Gln) and rs10050860 (p.Asp575Asn)). WT, wild type. Circles represent results for wild-type genotype samples, squares represent results for rs30187, upright triangles represent results for rs17482078 and inverted triangles refer to results for rs10050860.