Decoding the Papain Inhibitor from Streptomyces mobaraensis as Being Hydroxylated Chymostatin Derivatives: Purification, Structure Analysis, and Putative Biosynthetic Pathway

The Complete Genomic Sequence of Microbial Transglutaminase Producer, Streptomyces mobaraensis DSM40587

Actinomycetes are remarkable natural sources of active natural molecules and enzymes of considerable industrial value. Streptomyces mobaraensis is the first microorganism found to produce transglutaminase with broad industrial applications. Although transglutaminase in S. mobaraensis has been well studied over the past three decades, the genome of S. mobaraensis and its secondary metabolic potential were poorly reported. Here, we presented the complete genome of S. mobaraensis DSM40587 obtained from the German Collection of Microorganisms and Cell Cultures GmbH. It contains a linear chromosome of 7,633,041 bp and a circular plasmid of 23,857 bp. The chromosome with an average GC content of 73.49% was predicted to harbour 6683 protein-coding genes, seven rRNA and 69 tRNA genes. Comparative genomic analysis reveals its meaningful genomic characterisation. A comprehensive bioinformatics investigation identifies 35 putative BGCs (biosynthesis gene clusters) involved in synthesising various secondary metabolites. Of these, 13 clusters showed high similarity (> 55%) to known BGCs coding for polyketides, nonribosomal peptides, hopene, RiPP (Ribosomally synthesized and post-translationally modified peptides), and others. Furthermore, these BGCs with over 65% similarity to the known BGCs were analysed in detail. The complete genome of S. mobaraensis DSM40587 reveals its capacity to yield diverse bioactive natural products and provides additional insights into discovering novel secondary metabolites.

Approaching transglutaminase from Streptomyces bacteria over three decades

Transglutaminases are protein cross-linking and protein-modifying enzymes that have attracted considerable interest due to their causal involvement in various diseases and versatility in industrial applications. In particular, microbial transglutaminases (MTG) from Streptomyces bacteria have managed in recent years to evolve from simple food additives to specialized enzymes for the site-directed modification of therapeutic proteins. The review summarizes relevant studies from the beginning dealing with the occurrence, production, structure, catalysis, and substrate molecules of MTG enzymes. It also addresses biotechnological procedures with MTG from S. mobaraensis (SmMTG) as the most prominent representative in focus. Reassessment of the available data revealed unexpected insights into catalysis of SmMTG and other transglutaminases, suggesting selection of glutamine donor proteins by subsites at the front vestibule and the existence of distinct lysine pockets. Flexibility of the SmMTG-accessible glutamine donor substrate regions seems to be more important than the glutamine environment. Nevertheless, residues in close vicinity to glutamines also determine interaction with the SmMTG subsites. The apparent lack of subsites for lysine donor proteins suggests self-assembly of the substrate proteins prior to enzymatic cross-linking. The study of natural substrate proteins, especially their mutual interaction, is proposed to further illuminate catalysis of SmMTG. To this end, structure and function of the characterized substrate proteins from S. mobaraensis are discussed in conclusion.