The Inh inhibitor is secreted into the periplasm where its presumed physiological function is to protect periplasmic proteins against the action of secreted proteases [1]. A range of proteases including A, B and C from E. chrysanthemi, alkaline protease from Pseudomonas aeruginosa and the 50 kDa protease from Serratia marcescens are inhibited.

1: Crystal structure of a complex between Serratia marcescens metallo-protease and an inhibitor from Erwinia chrysanthemi. Baumann U, Bauer M, Letoffe S, Delepelaire P, Wandersman C; J Mol Biol 1995;248:653-661. PMID:7752231