title: A novel transglutaminase substrate from Streptomyces mobaraensis inhibiting papain-like cysteine proteases.
abstract: Transglutaminase from Streptomyces mobaraensis is an enzyme of unknown function that cross-links proteins to high molecular weight aggregates. Previously, we characterized two intrinsic transglutaminase substrates with inactivating activities against subtilisin and dispase. This report now describes a novel substrate that inhibits papain, bromelain, and trypsin. Papain was the most sensitive protease; thus, the protein was designated Streptomyces papain inhibitor (SPI). To avoid transglutaminase-mediated glutamine deamidation during culture, SPI was produced by Streptomyces mobaraensis at various growth temperatures. The best results were achieved by culturing for 30-50 h at 42 degrees C, which yielded high SPI concentrations and negligibly small amounts of mature transglutaminase. Transglutaminasespecific biotinylation displayed largely unmodified glutamine and lysine residues. In contrast, purified SPI from the 28 degrees C culture lost the potential to be cross-linked, but exhibited higher inhibitory activity as indicated by a significantly lower Ki (60 nM vs. 140 nM). Despite similarities in molecular mass (12 kDa) and high thermostability, SPI exhibits clear differences in comparison with all members of the wellknown family of Streptomyces subtilisin inhibitors. The neutral protein (pI of 7.3) shares sequence homology with a putative protein from Streptomyces lavendulae, whose conformation is most likely stabilized by two disulfide bridges. However, cysteine residues are not localized in the typical regions of subtilisin inhibitors. SPI and the formerly characterized dispase-inactivating substrate are unique proteins of distinct Streptomycetes such as Streptomyces mobaraensis. Along with the subtilisin inhibitory protein, they could play a crucial role in the defense of vulnerable protein layers that are solidified by transglutaminase.
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Applied Sciences of Darmstadt, Schnittspahnstrasse 12, Darmstadt, Germany.
authors.forename: Alla
authors.initials: A
authors.lastname: Sarafeddinov
authors.forename: Atia
authors.initials: A
authors.lastname: Arif
authors.forename: Anna
authors.initials: A
authors.lastname: Peters
authors.forename: Hans-Lothar
authors.initials: HL
authors.lastname: Fuchsbauer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification; D057056:Cysteine Proteases / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D008969:Molecular Sequence Data; D010206:Papain / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017385:Sequence Homology; D013302:Streptomyces / Q000145:classification / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D013379:Substrate Specificity; D011503:Transglutaminases / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D015853:Cysteine Proteinase Inhibitors; D011503:Transglutaminases; D057056:Cysteine Proteases; D010206:Papain