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Jeya, Marimuthu,Kim, Tae-Su,Kumar Tiwari, Manish,Li, Jinglin,Zhao, Huimin,Lee, Jung-Kul The Royal Society of Chemistry 2012 Molecular bioSystems Vol.8 No.12
<P>A novel type III polyketide synthase (RePKS) from <I>Rhizobium etli</I> produced a heptaketide pyrone using acetyl-CoA and six molecules of malonyl-CoA. Its catalytic efficiency (<I>k</I><SUB>cat</SUB>/<I>K</I><SUB>m</SUB> = 5230 mM<SUP>−1</SUP> min<SUP>−1</SUP>) for malonyl CoA was found to be the highest ever reported. Molecular dynamics studies revealed the unique features of RePKS.</P> <P>Graphic Abstract</P><P>A novel type III polyketide synthase (RePKS) from <I>Rhizobium etli</I> produced a heptaketide pyrone using acetyl-CoA and six molecules of malonyl-CoA. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2mb25347j'> </P>
Prabhu, Ponnandy,Jeya, Marimuthu,Lee, Jung-Kul American Society for Microbiology 2010 Applied and environmental microbiology Vol.76 No.5
<B>ABSTRACT</B><P><I>Bacillus licheniformis</I>l-arabinose isomerase (l-AI) is distinguished from other l-AIs by its high degree of substrate specificity for l-arabinose and its high turnover rate. A systematic strategy that included a sequence alignment-based first screening of residues and a homology model-based second screening, followed by site-directed mutagenesis to alter individual screened residues, was used to study the molecular determinants for the catalytic efficiency of <I>B. licheniformis</I>l-AI. One conserved amino acid, Y333, in the substrate binding pocket of the wild-type <I>B. licheniformis</I>l-AI was identified as an important residue affecting the catalytic efficiency of <I>B. licheniformis</I>l-AI. Further insights into the function of residue Y333 were obtained by replacing it with other aromatic, nonpolar hydrophobic amino acids or polar amino acids. Replacing Y333 with the aromatic amino acid Phe did not alter catalytic efficiency toward l-arabinose. In contrast, the activities of mutants containing a hydrophobic amino acid (Ala, Val, or Leu) at position 333 decreased as the size of the hydrophobic side chain of the amino acid decreased. However, mutants containing hydrophilic and charged amino acids, such as Asp, Glu, and Lys, showed almost no activity with l-arabinose. These data and a molecular dynamics simulation suggest that Y333 is involved in the catalytic efficiency of <I>B. licheniformis</I>l-AI.</P>
Lee, Kyoung-Mi,Jeya, Marimuthu,Joo, Ah-Reum,Singh, Raushan,Kim, In-Won,Lee, Jung-Kul Elsevier 2010 Enzyme and microbial technology Vol.46 No.3
<P><B>Abstract</B></P><P>A novel endo-β-1,4-glucanase (EG)-producing strain was isolated and identified as <I>Penicillium purpurogenum</I> KJS506 based on its morphology and internal transcribed spacer (ITS) rDNA gene sequence. <I>P. purpurogenum</I> produced one of the highest levels of EG (5.6Umg-protein<SUP>−1</SUP>) with rice straw and corn steep powder as carbon and nitrogen sources, respectively. The extracellular EG was purified to homogeneity by sequential chromatography of <I>P. purpurogenum</I> culture supernatants on a DEAE sepharose column, a gel filtration column, and then on a Mono Q column with fast protein liquid chromatography. The purified EG was a monomeric protein with a molecular weight of 37kDa and showed broad substrate specificity with maximum activity towards lichenan. <I>P. purpurogenum</I> EG showed <I>t</I><SUB>1/2</SUB> value of 2h at 70°C and catalytic efficiency of 118mlmg<SUP>−1</SUP>s<SUP>−1</SUP>, one of the highest levels seen for EG-producing microorganisms. Although EGs have been reported elsewhere, the high catalytic efficiency and thermostability distinguish <I>P. purpurogenum</I> EG.</P>