RRC ID 49277
著者 Taniguchi H, Sungwallek S, Chotchuang P, Okano K, Honda K.
タイトル A Key Enzyme of the NAD+ Salvage Pathway in Thermus thermophilus: Characterization of Nicotinamidase and the Impact of Its Gene Deletion at High Temperatures.
ジャーナル J Bacteriol
Abstract NAD (NAD+) is a cofactor related to many cellular processes. This cofactor is known to be unstable, especially at high temperatures, where it chemically decomposes to nicotinamide and ADP-ribose. Bacteria, yeast, and higher organisms possess the salvage pathway for reconstructing NAD+ from these decomposition products; however, the importance of the salvage pathway for survival is not well elucidated, except for in pathogens lacking the NAD+de novo synthesis pathway. Herein, we report the importance of the NAD+ salvage pathway in the thermophilic bacterium Thermus thermophilus HB8 at high temperatures. We identified the gene encoding nicotinamidase (TTHA0328), which catalyzes the first reaction of the NAD+ salvage pathway. This recombinant enzyme has a high catalytic activity against nicotinamide (Km of 17 μM, kcat of 50 s-1, kcat/Km of 3.0 × 103 s-1 · mM-1). Deletion of this gene abolished nicotinamide deamination activity in crude extracts of T. thermophilus and disrupted the NAD+ salvage pathway in T. thermophilus Disruption of the salvage pathway led to the severe growth retardation at a higher temperature (80°C), owing to the drastic decrease in the intracellular concentrations of NAD+ and NADH.IMPORTANCE NAD+ and other nicotinamide cofactors are essential for cell metabolism. These molecules are unstable and decompose, even under the physiological conditions in most organisms. Thermophiles can survive at high temperatures where NAD+ decomposition is, in general, more rapid. This study emphasizes that NAD+ instability and its homeostasis can be one of the important factors for thermophile survival in extreme temperatures.
巻・号 199(17)
公開日 2017-9-1
DOI 10.1128/JB.00359-17
PII JB.00359-17
PMID 28630126
PMC PMC5553036
MeSH Gene Deletion* Hot Temperature Kinetics NAD / metabolism* Niacinamide / metabolism Nicotinamidase / genetics Nicotinamidase / metabolism* Thermus thermophilus / enzymology* Thermus thermophilus / genetics Thermus thermophilus / growth & development Thermus thermophilus / radiation effects*
IF 3.006
引用数 8
リソース情報
遺伝子材料 pUC18-HTK (with promoter) (RDB03436) Thermus thermophilus expression plasmid TEx03C01 (THR001249).