PRIMARY STRUCTURE OF MICROBIAL TRANSGLUTAMINASE FROM STREPTOVERTICILLIUM SP STRAIN-S-8112

The complete amino acid sequence of transglutaminase (EC 2.3.2.13) (TG ase), which is produced by a microorganism, Streptoverticillium sp. st rain s-8112, and catalyzes the acyl transfer reaction between gamma-ca rboxyamide groups of glutamine residues in proteins and various primar y amines, has been established by a combination of fast atom bombardme nt mass spectrometry and standard Edman degradation of peptide fragmen ts produced by treatment of the TGase with various proteolytic enzymes and purified by a reversed-phase high performance liquid chromatograp hy. The TGase consists of 331 amino acid residues with a chemical mole cular weight of 37,863, in agreement with the observed molecular weigh t (37,869.2 +/- 8.8) determined from its electrospray ionization mass spectrum. The sequence of the enzyme is very different from those of m ammalian TGases represented by guinea pig liver enzyme. The enzyme con tains a sole Cys residue, which is essential for its catalytic activit y. Hydropathy analysis indicated that the secondary structure of the r egion around the active site Cys residue is similar to those of mammal ian TGases. These results suggest that this microbial protein evolved by a different pathway from that of mammalian TGases and acquired acyl transfer activity during the evolutional process.