6k96

Publication Abstract from PubMed

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 (6S)-d-[6-(2)H1]- and (6R)-d-[6-(2)H1]glucose in the aristeromycin-producing strain Streptomyces citricolor. We observed retention of the (2)H atom of (6S)-d-[6-(2)H1]glucose and no incorporation of the (2)H atom from (6R)-d-[6-(2)H1]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 (6S)-d-[6-(2)H1]- and (6R)-d-[6-(2)H1]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.

Stereochemistry in the Reaction of the myo-Inositol Phosphate Synthase Ortholog Ari2 during Aristeromycin Biosynthesis.,Kudo F, Tsunoda T, Yamaguchi K, Miyanaga A, Eguchi T Biochemistry. 2019 Dec 24;58(51):5112-5116. doi: 10.1021/acs.biochem.9b00981., Epub 2019 Dec 13. PMID:31825604^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.