Characterization of a mannose-6-phosphate isomerase from Thermus thermophilus and increased L-ribose production by its R142N mutant

Applied and Environmental Microbiology
Soo-Jin YeomDeok-Kun Oh

Abstract

An uncharacterized gene from Thermus thermophilus, thought to encode a mannose-6-phosphate isomerase, was cloned and expressed in Escherichia coli. The maximal activity of the recombinant enzyme for L-ribulose isomerization was observed at pH 7.0 and 75°C in the presence of 0.5 mM Cu(2+). Among all of the pentoses and hexoses evaluated, the enzyme exhibited the highest activity for the conversion of L-ribulose to L-ribose, a potential starting material for many L-nucleoside-based pharmaceutical compounds. The active-site residues, predicted according to a homology-based model, were separately replaced with Ala. The residue at position 142 was correlated with an increase in L-ribulose isomerization activity. The R142N mutant showed the highest activity among mutants modified with Ala, Glu, Tyr, Lys, Asn, or Gln. The specific activity and catalytic efficiency (k(cat)/K(m)) for L-ribulose using the R142N mutant were 1.4- and 1.6-fold higher than those of the wild-type enzyme, respectively. The k(cat)/K(m) of the R142N mutant was 3.8-fold higher than that of Geobacillus thermodenitrificans mannose-6-phosphate isomerase, which exhibited the highest activity to date for the previously reported k(cat)/K(m). The R142N mutant enzyme pro...Continue Reading

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Citations

Oct 5, 2014·Applied Microbiology and Biotechnology·Zheng XuHong Xu
Feb 22, 2012·Journal of Industrial Microbiology & Biotechnology·Koen BeerensWim Soetaert
Aug 30, 2011·Applied Microbiology and Biotechnology·Chao HuCuiying Hu
Jan 1, 2015·Microorganisms·Olalla López-LópezMaría-Isabel González-Siso
May 7, 2020·Applied Microbiology and Biotechnology·Jiajun ChenWanmeng Mu
Jun 26, 2020·The Journal of Microbiology·Soo-Jung KimSoo-Jin Yeom

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