Isolation and characterization of a salt-tolerant γ-glutamyl transpeptidase from xerophilic .

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Xerophilic molds isolated from halo-alkaliphilic and dry environments are attractive genetic resources for obtaining salt- and osmo-adaptive enzymes. MA0196 secreted the largest amount of γ-glutamyl transpeptidase (GGT) during solid-state fermentation at a low initial water activity (  = 0.85). Gel filtration analysis revealed that the molecular mass of the purified native enzyme (MA0196 GGT) was 120 kDa. SDS-PAGE analysis showed that MA0196 GGT consists of two subunits with molecular masses of 56.4 and 33 kDa, indicating production from a proenzyme via autoproteolysis. Deglycosylation of the subunits by -glycosidase F yielded 40.9 and 19.6 kDa species. MA0196 GGT retained transpeptidase and hydrolysis activities and their catalytic efficiency ( / ) under high salt and low water activity. The enzyme displayed broad substrate specificity toward γ-glutamyl acceptors such as amino acids and the imidazole dipeptides, carnosine and anserine. Carnosine and L-glutamine were converted into γ-glutamyl-β-alanyl-L-histidine by MA0196 GGT with a 32.9% yield in the presence of 2% (v/v) dimethyl sulfoxide. Phylogenetic analysis indicated that MA0196 GGT forms a distinct lineage from and GGTs. These excellent properties indicate that MA0196 GGT can be used in salted fermentation and for producing bioactive peptides.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-022-03259-3.