Application of Hyperthennophilir 2-Deoxy-D-Riltose-5-Phosphate Aldolase

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Genes encoding 2-deoxy-D-ribose-5-phosphate aldolase (DERA) homologues from two hyperthermophiles, the archaeon Pyrobaculum aerophilum and the bacterium Thermotoga maritima, were expressed individually Eschelichia coli, after which the structures and activities of the enzymes produced were characterized and compared with those of E. coli DERA. lb our surprise, the two hyperthermophilic DERAs showed much greater catalysis of sequential aldol condensation using three acetaldehydes as substrates than the E coli enzyme, even at a low temperature (25℃), though both showed much less 2-deoxy-D-ribose-5-phosphate synthetic activity. Both the enzymes were highly resistant to high concentration of acetaldehyde and retained about 50% of their initial activities after 20-hours exposure to 300 mM acetaldehyde at 25℃, whereas the E coli DERA is almost completely inactivated after 2-hours exposure under the same conditions.The structure of the P. aerophilum DERA was determined by x-ray crystallography to a resolution of 2.0A. The mainchain coordinate of the P. aerophilum enzyme monomer was quite similar to those of the T maritime and E call enzymes, whose crystal structures have been already solved. However, the quaternary structure of the hyperthermophilic enzymes was totally different from that of the E coli DERA. The area of the subunit-subunit interface in the dimer of the hyperthermophilic enzymes are much larger compared with the E coif enzyme. This promotes the formation of the unique dimeric structure and strengthens the hydrophobic inter subunit interactions. These structural features are considered to be responsible for the extremely high stability of the hyperthermophilic DERAs.