Inhibition of bacterial transglutaminase by its heat-treated pro-enzyme

Transglutaminases form a unique family of cross-linking enzymes which may be interesting for pharmaceutical and technical purposes. Bacterial transglutaminase, differing from the eucaryotic counterparts in being independent from Ca2+ ions, is excreted by several Streptomyces species. Until now an endogenous factor regulating activated transglutaminase could not be detected. Here, we investigated whether an inhibitor of transglutaminase is excreted into the culture fluid of Streptomyces mobaraensis. We could demonstrate that heat-resistant inhibitory activity is produced after 24h of growth reaching a maximum after 72h. A two-step ion exchange chromatography purification procedure revealed co-elution of the heat-treated inhibitor with pro-transglutaminase. Experiments with wild-type and recombinant pro-transglutaminase confirmed that the precursor protein indeed inhibits the activity of the mature enzyme.