• BMB Reports
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• v.40 no.5
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• pp.801-804
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• 2007

The products of reactions catalyzed by Methanococcus. jannaschii (Mj) aldolase using various substrates were identified by gas chromatography (GC). Although Mj aldolase is considered a fuculose-1-phosphate aldolase based on homology searching after gene sequencing, it has not been proven to be a fuculose-1-phosphate aldolase based on its reaction products. Mj aldolase was found to catalyze reactions between glycoaldehyde or D, L-glyceraldehyde and DHAP (dihydroxyacetone phosphate). Before performing GC the ketoses produced were converted into peracetylated alditol derivatives by sequential reactions, i.e., dephosphorylation, $NaBH_4$ reduction, and acetylation. By comparing the GC data of final products with those of standard alditol samples, it was found that the enzymatic reactions with glycoaldehyde, D-glyceraldehyde, and D, L-glyceraldehyde produced D-ribulose-1-phosphate, D-psicose-1-phosphate, and a mixture of D-psicose and L-tagatose-1-phosphate, respectively. These results provide direct evidence that Mj aldolase is a fuculose-1-phosphate aldolase.

• Journal of Microbiology and Biotechnology
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• v.11 no.5
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• pp.838-844
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• 2001

The enzyme Fuc aldolase from Methanococcus jannaschii that catalyzes the aldol condensation of DHAP and L-lactaldehyde to give fuculose-1-phosphate was inactivated by DEP. The inactivation was pseudo first-order in the enzyme and DEP, which was biphasic. A pseudo second-order rate constant of 120$M^{-1}min^{-1}$ was obtained at pH 6.0 and $25{\circ}C$. Quantifying the increase in absorbance at 240nm showed that four histidine residues per subunit were modified during the nearly complete inactivation. The statistical analysis and the time course of the modification suggested that two or three histidine residues were essential for activity. The rate of inactivation was dependent on the pH, and the pH inactivation data implied the involvement of the amino acid residue with a $pK_a$ value of 5.7. Fuc aldolase was protected against DEP inactivation by DHAP, indicating that the histidine residues were located at the active site of Fuc aldolase. DL-Glyceraldehyde, as an alternative substrate to L-lactaldehyde, showed no specific protection for the Fuc aldolase.

• Journal of Microbiology and Biotechnology
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• v.11 no.4
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• pp.709-711
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• 2001

To elucidate the putative role of the amido group in the metal binding of the fuculose-1-phosphate aldolase from Methanococcus jannaschii, we have examined a potential targen using site-directed mutagenesis. The replacement of asparagine 25 with leucine or threonine was shown to have a negative effect, not only on catlytic efficiency, but also on substrage recognition as well. The Hill coefficient values yeilded a value of =1. All metals used with the wild-type aldolases exhibited higher activity than that of the mutants. The spectra of the mutants were quite different from the wild-type aldolase. A highly conserved amino acid of asparagine 25 in a related family of aldolase odes not appear to provide sufficient evidence for evolution.