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Background  Transglutaminases (TGase), synthesized as a zymogen (pro-TGase) in  Streptomyces  sp., are important enzymes in food industry. Due to the important applications of TGase in food industry, obtaining robust and food-safe TGase-producing strains has attracted much attention during the past decade. In this study,  Streptomyces hygroscopicus  pro-TGase was efficiently expressed and secreted by a food-grade host,  Yarrowia lipolytica , without antibiotic markers.    Results  The pro-TGase gene was cloned into integrative vectors pINA1296 (monocopy) and pINA1297 (multicopy), and was used to transform the  Y. lipolytica  Po1g or Po1h strain, respectively. Expression was driven by a recombinant hp4d promoter and secretion obtained using a  XPR2  pre-sequence as a signal peptide. The highest yield of extracellular pro-TGase produced by the recombinant Po1h strain corresponded to 5.3 U/mL of TGase, a level 8.8 fold higher than that obtained using the recombinant Po1g strain. Asparagines in two potential Asn-linked glycosylation sites (Asn160 and Asn355) from pro-TGase were mutated to glutamine individually or simultaneously, yielding the deglycosylated variants N160Q, N355Q, and N160Q/N355Q. The activities of N160Q, N355Q and N160Q/N355Q constructs were respectively 5.3 U/mL, 7.8 U/mL, and 3.0 U/mL, equivalent to 100 %, 147 %, and 57 % of that from wild-type pro-TGase. The TGase yield of N355Q variant was raised to 35.3 U/mL of by using a glycerol feeding strategy in a 3 L fermenter. The optimal pH and temperature of the activated pro-TGase, and of its deglycosylated variants, were in the range of 5.0-6.0 pH and 40-45 °C, respectively. The half-life of the recombinant wild-type pro-TGase at 37 °C reached 34.0 min, and those of the variants were from 24.2 min to 11.5 min. In contrast to the wild-type pro-TGase, all of the variants had decreased specific activities, and both the  K  m  and  k  cat  values of the variants decreased accordingly.    Conclusions  This study constitutes the first report of the heterologous expression of a pro-TGase in  Y. lipolytica , and provides new possibilities for the efficient production of TGases used in food processing.

Overproduction of pro-transglutaminase from Streptomyces hygroscopicus in Yarrowia lipolytica and its biochemical characterization