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Parajuli, Niranjan,Basnet, Devi B.,Chung, Young Soo,Lee, Hei Chan,Liou, Kwangkyoung,Sohng, Jae Kyung Elsevier 2005 Enzyme and microbial technology Vol.37 No.4
<P><B>Abstract</B></P><P>We have found that the thermophilic activity of glucose-1-phosphate thymidylyltransferase (stRmlA) is conditional upon the presence certain substances. In particular, it showed its thermal stability only in the presence of 50mM dTTP or dTMP, thermal stability being the highest at 70°C. The purified enzyme was stable up to 90°C within a broad pH range from 2.0 to 13.0, and its maximum activity was measured at a pH of 11.5 at 70°C. Unlike other mesophilic counterparts, it showed catalytic activity in the presence of various metal ions in the following order of reactivity: Mg<SUP>2+</SUP>>Zn<SUP>2+</SUP>>Cu<SUP>2+</SUP>>Co<SUP>2+</SUP>>Fe<SUP>2+</SUP>>Ca<SUP>2+</SUP>>Fe<SUP>3+</SUP>>Ni<SUP>2+</SUP>. Its catalytic activity was not inhibited even by the denaturants 50mM guanidine hydrochloride and 50mM urea.</P><P>To explore the molecular basis for its unusual thermostability, homology structural modeling, codon usage comparisons, and amino acid composition analyses were performed. The CCC, CUC and UCC codons are significantly higher, and distributed uniformly in <I>strmlA</I> as contrasted with other GPTTs. Our analyses revealed that the GC rich coding sequences may not be the reason for thermostability of stRmlA. The β-sheets are also found more likely in stRmlA, which contributes to thermal stability by increasing the number of hydrogen bonds. Further results suggest that a large number of apolar functional groups exposed to solvent accessible surface area, a significant number of residues sensitive to oxidation or deamination, and a higher hydrophobicity, any or all of the which could be reasons for its unique thermophilic behavior. Finally, we postulate that dTTP or dTMP enters the active site and binds tightly to inhibit the defolding of the protein, which, in turn, increases its thermal stability. Such findings will be useful for further investigations on thermophilic behavior of enzymes.</P>
Diversity of Cytochrome P450 in Streptomyces peucetius
Parajuli, Niranjan,Basnet, Devi B.,Kim, Byung-Gee,Lee, Hei Chan,Sohng, Jae Kyung,Liou, Kwangkyoung 한국공업화학회 2004 응용화학 Vol.8 No.1
We have determined the genome sequences of 8.7 Mb chromosome of Streptomyces peucetiusATCC 27952, which produces clinically important anthracyline chemotherapeutic agents of the polyketide class of antibiotics, daunorubicin and doxorubicin. The cytochrome P450 gene superfamily is represented by 19 sequences in the S. peucetius. Amongthose, 15 code for apparently functional genes whereas four are apparently pseudo genes. Four cytochrome P450s are associated with modular PKS of avermectin, and two with doxorubicin biosynthetic gene cluster. CYP252A1 is the new family found in S. peucetius, which shares 38% identity to CYP51 from Streptomyces coelicolor A3 (2).
Structural Diversification of Macrolactones by Substrate-Flexible Cytochrome P450 Monooxygenases
Lee, Sang ,Kil,Basnet, Devi ,B.,Hong, Jay ,Sung ,Joong,Jung, Won ,Seok,Choi, Cha ,Yong,Lee, Hei ,Chan,Sohng, Jae ,Kyung,Ryu, Keun ,Garp,Kim, Dae WILEY-VCH 2005 Advanced Synthesis & Catalysis Vol.347 No.10
<P>The substrate flexibilities of several cytochrome P450 monooxygenases involved in macrolide biosynthesis were investigated to test their potential for the generation of novel macrolides. PikC hydroxylase in the pikromycin producer Streptomyces venezuelae accepted oleandomycin as an alternative substrate and introduced a hydroxy group at the C-4 position, which is different from the intrinsic C-12 hydroxylation position in the natural substrate. This is the first report of C-4 hydroxylation activity of cytochrome P450 monooxygenase involved in the biosynthesis of 14-membered macrolides. EryF hydroxylase from the erythromycin biosynthetic pathway of Saccharopolyspora erythraea and OleP oxidase from the oleandomycin biosynthetic pathway of Streptomyces antibioticus also showed a certain degree of plasticity towards alternative substrates. In particular, EryF and OleP were found to oxidize a 12-membered macrolactone as an alternative substrate. These results demonstrate the potential usefulness of these enzymes to diversify macrolactones by post-PKS oxidations.</P>
Kharel, Madan K,Basnet, Devi B,Lee, Hei Chan,Liou, Kwangkyoung,Moon, Young Ho,Kim, Jae-Jong,Woo, Jin Suk,Sohng, Jae Kyung Korean Society for Molecular Biology 2004 Molecules and cells Vol.18 No.1
<P>The organization of the 2-deoxystreptamine (DOS) biosynthetic gene cluster of Micromonospora echinospora has been determined. Sequencing of a 14.04 kb-region revealed twelve open reading frames (ORFs): four putative DOS biosynthetic genes (gtmA, B, C, and D), five amino sugars biosynthetic genes (gtmE, G, H, I, and gacB), two aminoglycoside resistance genes (gtmF and J) as well as a hypothetical ORF (gacA). One of the putative DOS biosynthetic genes, gtmA, was expressed in Escherichia coli, and the purified protein was shown to convert glucose-6-phosphate (G-6-P) to 2-deoxy-scyllo-inosose (DOI), a key step in DOS biosynthesis. In addition gtmJ was expressed in Streptomyces lividans and shown to confer gentamicin resistance. Thus gtmA and gtmJ are implicated in the biosynthesis of gentamicin and in resistance to it, respectively.</P>
송재경,Madan K. Kharel,Devi B. Basnet,Hei Chan Lee,류광경,Young Ho Moon,Jae-Jong Kim,Jin Suk Woo 한국분자세포생물학회 2004 Molecules and cells Vol.18 No.1
The organization of the 2-deoxystreptamine (DOS) biosynthetic gene cluster of Micromonospora echinospora has been determined. Sequencing of a 14.04 kb-region revealed twelve open reading frames (ORFs): four putative DOS biosynthetic genes (gtmA, B, C, and D), five amino sugars biosynthetic genes (gtmE, G, H, I, and gacB), two aminoglycoside resistance genes (gtmF and J) as well as a hypothetical ORF (gacA). One of the putative DOS biosynthetic genes, gtmA, was expressed in Escherichia coli, and the purified protein was shown to convert glucose-6-phosphate (G-6-P) to 2-deoxyscyllo- inosose (DOI), a key step in DOS biosynthesis. In addition gtmJ was expressed in Streptomyces lividans and shown to confer gentamicin resistance. Thus gtmA and gtmJ are implicated in the biosynthesis of gentamicin and in resistance to it, espectively.