PDI modified covalently with MMTS showed a significant
reduction in oxidoreductase activity, but its chaperone activity
was unaffected. However, both unmodified and
MMTS-treated PDI significantly increased the rate of tissue
factor-dependent factor Xa generation in a chromogenic assay
(99, 109). Furthermore, the wasp venom-derived peptide
mastoparan, which binds in the b¢ hydrophobic pocket of PDI
necessary for chaperone activity, inhibited the ability of bovine
PDI to enhance factor Xa generation. PDI treated with
N-ethylmaleimide enhanced factor Xa generation in a manner
similar to unmodified PDI (86).