Maggot chymotrypsin I from Lucilia sericata is resistant to endogenous wound protease inhibitors

Summary Background  A chymotrypsin found in the secretions of Lucilia sericata and manufactured as a recombinant enzyme degrades chronic wound eschar ex vivo . Objectives  To characterize the inhibition profile of the L. sericata recombinant chymotrypsin I. Methods  Activity of recombinant chymotrypsin I and its sensitivity to endogenous inhibitors were determined enzymatically using the fluorogenic substrate succinyl‐alanyl‐alanyl‐prolyl‐phenylalanyl‐aminomethyl coumarin. Results  We report the presence of high concentrations of two endogenous inhibitors, α1‐antichymotrypsin and α1‐antitrypsin, in wound eschar and a trace of a third, α2‐macroglobulin, with the potential to inhibit this debridement process. However, the addition of a soluble and inhibitor‐containing extract of chronic wound eschar to chymotrypsin I did not affect activity of the enzyme, neither did the addition of purified native α1‐antichymotrypsin or α1‐antitrypsin, although chymotrypsin I was inhibited by α2‐macroglobulin. Conversely, the mammalian equivalent, α‐chymotrypsin, was inhibited by the purified native α1‐antichymotrypsin, α1‐antitrypsin and α2‐macroglobulin and by the soluble extract of wound eschar. Conclusions  The data suggest that the maggot‐derived chymotrypsin I is biochemically distinct from human α‐chymotrypsin and the lack of inhibition by wound eschar suggests a means by which chymotrypsin I activity survives within the wound to contribute towards debridement during maggot biotherapy.