Identification of a novel d‐amino acid aminotransferase involved in d‐glutamate biosynthetic pathways in the hyperthermophile Thermotoga maritima. (8th April 2022)

• Record Type: Journal Article
• Authors: Miyamoto, Tetsuya; Moriya, Toshiyuki; Katane, Masumi; Saitoh, Yasuaki; Sekine, Masae; Sakai‐Kato, Kumiko; Oshima, Tairo; Homma, Hiroshi
• Is Part Of: FEBS journal. Volume 289:Number 19(2022)
• Page Start: 5933
• Page End: 5946
• Publication Date: 2022-04-08
• Subjects: Amino acid racemase -- d‐amino acid -- d‐amino acid aminotransferase -- d‐Glutamate -- Thermotoga maritima; Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.16452
• Languages: English
• ISSNs: 1742-464X

Abstract

Abstract : The hyperthermophilic bacterium Thermotoga maritima has an atypical peptidoglycan that contains d ‐lysine alongside the usual d ‐alanine and d ‐glutamate. We previously identified a lysine racemase involved in d ‐lysine biosynthesis, and this enzyme also possesses alanine racemase activity. However, T . maritima has neither alanine racemase nor glutamate racemase enzymes; hence, the precise biosynthetic pathways of d ‐alanine and d ‐glutamate remain unclear in T . maritima . In the present study, we identified and characterized a novel d ‐amino acid aminotransferase (TM0831) in T . maritima . TM0831 exhibited aminotransferase activity towards 23 d ‐amino acids, but did not display activity towards l ‐amino acids. It displayed high specific activities towards d ‐homoserine and d ‐glutamine as amino donors. The most preferred acceptor was 2‐oxoglutarate, followed by glyoxylate. Additionally, TM0831 displayed racemase activity towards four amino acids including aspartate and glutamate. Catalytic efficiency ( k cat / K m ) for aminotransferase activity was higher than for racemase activity, and pH profiles were distinct between these two activities. To evaluate the functions of TM0831, we constructed a TTHA1643 (encoding glutamate racemase)‐deficient Thermus thermophilus strain ( ∆TTHA1643 ) and integrated the TM0831 gene into the genome of ∆TTHA1643 . The growth of this TM0831 ‐integrated strain was promoted compared with ∆TTHA1643 and was restored to almost the same level as that of the wild‐type strain. These results suggest that TM0831 is involved in d ‐glutamate production. TM0831 is a novel d ‐amino acid aminotransferase with racemase activity that is involved in the production of d ‐amino acids in T . maritima . Abstract : TM0831 is a novel d ‐amino acid aminotransferase in Thermotoga maritima . It exhibits broad and unique substrate specificity for aminotransferase activity, and it possesses amino acid racemase activity towards several amino acids. Furthermore, TM0831 recovered the growth of a Glu racemase‐deficient Thermus thermophilus strain. Thus, TM0831 is presumably involved in the production of intracellular d ‐Glu.