A Novel Transglutaminase Substrate from Streptomyces mobaraensis Triggers Autolysis of Neutral Metalloproteases

Abstract

Transglutaminase (TGase) from Streptomyces mobaraensis is a Ca²⁺ independent enzyme that cross-links proteins to high molecular weight aggregates. A dispase autolysis inducing protein (DAIP) was identified as an intrinsic TGase substrate exhibiting accessible glutamine and lysine residues. DAIP modification during culture by TGase resulted in deamidation of reactive glutamines, formation of glutamic/lysine residue pairs, and failure of cross-linking. The reactivity of modified DAIP can be restored to some extent by N-lauroylamido-3-N′,N′-dimethylpropyl amine, thus exposing concertedly buried glutamines and lysines. The novel TGase substrate differs considerably from the well known Streptomyces subtilisin inhibitors in higher molecular mass (37 kDa), lower pI (7.1–7.2), moderate thermo-stability, and the mode of erasing dispase activity. Our experiments suggested that DAIP induces autolysis without removal of essential metals, such as Ca²⁺ and Zn²⁺. Among other endoproteases, only thermolysin was similarly affected, but at considerably higher DAIP concentrations, due to simultaneous degradation of DAIP.