Metabolism Dealing with Thermal Degradation of NAD + in the Hyperthermophilic Archaeon Thermococcus kodakarensis.

Autor:	Hachisuka SI; Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto, Japan.; JST, CREST, Gobancho, Tokyo, Japan., Sato T; Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto, Japan.; JST, CREST, Gobancho, Tokyo, Japan., Atomi H; Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto, Japan atomi@sbchem.kyoto-u.ac.jp.; JST, CREST, Gobancho, Tokyo, Japan.
Jazyk:	angličtina
Zdroj:	Journal of bacteriology [J Bacteriol] 2017 Sep 05; Vol. 199 (19). Date of Electronic Publication: 2017 Sep 05 (Print Publication: 2017).
DOI:	10.1128/JB.00162-17
Abstrakt:	NAD + is an important cofactor for enzymatic oxidation reactions in all living organisms, including (hyper)thermophiles. However, NAD + is susceptible to thermal degradation at high temperatures. It can thus be expected that (hyper)thermophiles harbor mechanisms that maintain in vivo NAD + concentrations and possibly remove and/or reuse undesirable degradation products of NAD + Here we confirmed that at 85°C, thermal degradation of NAD + results mostly in the generation of nicotinamide and ADP-ribose, the latter known to display toxicity by spontaneously linking to proteins. The hyperthermophilic archaeon Thermococcus kodakarensis possesses a putative ADP-ribose pyrophosphatase (ADPR-PPase) encoded by the TK2284 gene. ADPR-PPase hydrolyzes ADP-ribose to ribose 5-phosphate (R5P) and AMP. The purified recombinant TK2284 protein exhibited activity toward ADP-ribose as well as ADP-glucose. Kinetic analyses revealed a much higher catalytic efficiency toward ADP-ribose, suggesting that ADP-ribose was the physiological substrate. To gain insight into the physiological function of TK2284, a TK2284 gene disruption strain was constructed and examined. Incubation of NAD + in the cell extract of the mutant strain at 85°C resulted in higher ADP-ribose accumulation and lower AMP production compared with those in experiments with the host strain cell extract. The mutant strain also exhibited lower cell yield and specific growth rates in a synthetic amino acid medium compared with those of the host strain. The results obtained here suggest that the ADPR-PPase in T. kodakarensis is responsible for the cleavage of ADP-ribose to R5P and AMP, providing a means to utilize the otherwise dead-end product of NAD + breakdown. IMPORTANCE Hyperthermophilic microorganisms living under high temperature conditions should have mechanisms that deal with the degradation of thermolabile molecules. NAD + is an important cofactor for enzymatic oxidation reactions and is susceptible to thermal degradation to ADP-ribose and nicotinamide. Here we show that an ADP-ribose pyrophosphatase homolog from the hyperthermophilic archaeon Thermococcus kodakarensis converts the detrimental ADP-ribose to ribose 5-phosphate and AMP, compounds that can be directed to central carbon metabolism. This physiological role for ADP-ribose pyrophosphatases might be universal in hyperthermophiles, as their homologs are widely distributed among both hyperthermophilic bacteria and archaea. (Copyright © 2017 American Society for Microbiology.)
Databáze:	MEDLINE
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