6K96

Stereochemistry in the Reaction of themyo-Inositol Phosphate Synthase Ortholog Ari2 during Aristeromycin Biosynthesis.

(2019) Biochemistry 58: 5112-5116

• PubMed: 31825604 Search on PubMed
• DOI: https://doi.org/10.1021/acs.biochem.9b00981
• Primary Citation of Related Structures:  
  6K96


• PubMed Abstract: 
  

  The myo -inositol-1-phosphate synthase (MIPS) ortholog Ari2, which is encoded in the aristeromycin biosynthetic gene cluster, catalyzes the formation of five-membered cyclitol phosphate using d-fructose 6-phosphate (F6P) as a substrate. To understand the stereochemistry during the Ari2 reaction in vivo , we carried out feeding experiments with (6 S )-d-[6- ² H ₁ ]- and (6 R )-d-[6- ² H ₁ ]glucose in the aristeromycin-producing strain Streptomyces citricolor . We observed retention of the ² H atom of (6 S )-d-[6- ² H ₁ ]glucose and no incorporation of the ² H atom from (6 R )-d-[6- ² H ₁ ]glucose in aristeromycin. This indicates that Ari2 abstracts the pro-R proton at C6 of F6P after oxidation of C5-OH by nicotinamide adenine dinucleotide (NAD ⁺ ) to generate the enolate intermediate, which then attacks the C2 ketone to form the C-C bond via aldol-type condensation. The reaction of Ari2 with (6 S )-d-[6- ² H ₁ ]- and (6 R )-d-[6- ² H ₁ ]F6P in vitro exhibited identical stereochemistry compared with that observed during the feeding experiments. Furthermore, analysis of the crystal structure of Ari2, including NAD ⁺ as a ligand, revealed the active site of Ari2 to be similar to that of MIPS of Mycobacterium tuberculosis , supporting the similarity of the reaction mechanisms of Ari2 and MIPS.

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Organizational Affiliation: 

Department of Chemistry , Tokyo Institute of Technology , 2-12-1, O-okayama , Meguro-ku, Tokyo 152-8551 , Japan.