Graduate School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
FEBS Lett. 2021 Dec;595(23):2931-2941. doi: 10.1002/1873-3468.14222. Epub 2021 Nov 16.
The hyperthermophilic bacterium Thermotoga maritima peptidoglycan contains unusual d-lysine alongside typical d-alanine and d-glutamate. We previously identified lysine racemase and threonine dehydratase, but knowledge of d-amino acid metabolism remains limited. Herein, we identified and characterized T. maritima acetylornithine aminotransferase TM1785. The enzyme was most active towards acetyl-l-ornithine, but also utilized l-glutamate, l-ornithine and acetyl-l-lysine as amino donors, and 2-oxoglutarate was the preferred amino acceptor. TM1785 also displayed racemase activity towards four amino acids and lyase activity towards l-cysteine, but no dehydratase activity towards l-serine, l-threonine or corresponding d-amino acids. Catalytic efficiency (k /K ) was highest for aminotransferase activity and lowest for racemase activity. TM1785 is a novel acetylornithine aminotransferase associated with l-arginine biosynthesis that possesses two additional distinct activities.
嗜热海洋杆菌的肽聚糖含有不寻常的 D-赖氨酸，以及典型的 D-丙氨酸和 D-谷氨酸。我们之前已经鉴定了赖氨酸消旋酶和苏氨酸脱水酶，但对 D-氨基酸代谢的了解仍然有限。在此，我们鉴定并表征了嗜热海洋杆菌乙酰鸟氨酸氨基转移酶 TM1785。该酶对乙酰-L-鸟氨酸的活性最高，但也能利用 L-谷氨酸、L-鸟氨酸和乙酰-L-赖氨酸作为氨基供体，而 2-氧代戊二酸是首选的氨基受体。TM1785 对四种氨基酸具有消旋酶活性，对 L-半胱氨酸具有裂解酶活性，但对 L-丝氨酸、L-苏氨酸或相应的 D-氨基酸没有脱水酶活性。对于氨基转移酶活性，催化效率（k /K ）最高，对于消旋酶活性，催化效率最低。TM1785 是一种与 L-精氨酸生物合成相关的新型乙酰鸟氨酸氨基转移酶，具有另外两种独特的活性。
