Identification of a species-specific aminotransferase in Pediococcus acidilactici capable of forming α-aminobutyrate

Alexander Wenger; Remo S Schmidt; Reto Portmann; Alexandra Roetschi; Elisabeth Eugster; Laure Weisskopf; Stefan Irmler

doi:10.1186/s13568-020-01034-2

Identification of a species-specific aminotransferase in Pediococcus acidilactici capable of forming α-aminobutyrate

AMB Express. 2020 May 29;10(1):100. doi: 10.1186/s13568-020-01034-2.

Authors

Alexander Wenger^{1

2}, Remo S Schmidt¹, Reto Portmann¹, Alexandra Roetschi¹, Elisabeth Eugster³, Laure Weisskopf², Stefan Irmler⁴

Affiliations

¹ Agroscope, Schwarzenburgstrasse 161, 3003, Bern, Switzerland.
² Department of Biology, University of Fribourg, Rue Albert-Gockel 3, 1700, Fribourg, Switzerland.
³ Bern University of Applied Sciences, School of Agricultural, Forest, and Food Sciences HAFL, Länggasse 85, 3052, Zollikofen, Switzerland.
⁴ Agroscope, Schwarzenburgstrasse 161, 3003, Bern, Switzerland. stefan.irmler@agroscope.admin.ch.

Abstract

During cheese ripening, the bacterial strain Pediococcus acidilactici FAM18098 produces the non-proteinogenic amino acid, α-aminobutyrate (AABA). The metabolic processes that lead to the biosynthesis of this compound are unknown. In this study, 10 P. acidilactici, including FAM18098 and nine Pediococcus pentosaceus strains, were screened for their ability to produce AABA. All P. acidilactici strains produced AABA, whereas the P. pentosaceus strains did not. The genomes of the pediococcal strains were sequenced and searched for genes encoding aminotransferases to test the hypothesis that AABA could result from the transamination of α-ketobutyrate. A GenBank and KEGG database search revealed the presence of a species-specific aminotransferase in P. acidilactici. The gene was cloned and its gene product was produced as a His-tagged fusion protein in Escherichia coli to determine the substrate specificity of this enzyme. The purified recombinant protein showed aminotransferase activity at pH 5.5. It catalyzed the transfer of the amino group from leucine, methionine, AABA, alanine, cysteine, and phenylalanine to the amino group acceptor α-ketoglutarate. Αlpha-ketobutyrate could replace α-ketoglutarate as an amino group acceptor. In this case, AABA was produced at significantly higher levels than glutamate. The results of this study show that P. acidilactici possesses a novel aminotransferase that might play a role in cheese biochemistry and has the potential to be used in biotechnological processes for the production of AABA.

Keywords: Aminotransferase; Pediococcus acidilactici; α-Aminobutyrate; α-Ketobutyrate.