Fluorometabolite biosynthesis: isotopically labelled glycerol incorporations into the antibiotic nucleocidin in Streptomyces calvus

Abstract

Deuterium and carbon-13 labelled glycerols have been fed to Streptomyces calvus fermentations and isotope incorporation into the fluorine containing antibiotic nucleocidin have been evaluated by F-NMR. A single deuterium atom was incorporated from [H]- and (R)-[H]-glycerol into C-5' of the antibiotic, suggesting that an oxidation occurs at this carbon after ribose ring assembly from glycerol (pentose phosphate pathway), during nucleocidin biosynthesis.

Incorporation of [2H1]-(1R,2R)- and [2H1]-(1S,2R)-glycerols into the antibiotic nucleocidin in Streptomyces calvus

“…The mechanism by which the fluorine becomes incorporated into nucleocidin 1 remains to be evaluated. However it follows from these observations that there is no evidence to suggest an obligate oxidation at C-5' of the ribose moiety of an adenosine precursor during nucleocidin 1 biosynthesis as previously implied, 9 as there is a population of nucleocidin molecules carrying two deuterium atoms at C-5' after [ 2 H5]-glycerol 2c incorporation. The retention of both hydrogens from the pro-(R) hydroxymethyl arm of glycerol into nucleocidin 1 is illustrated in Scheme 1, with the stereochemistry shown consistent with the pentose phosphate pathway.…”

“…two deuteriums were incorporated at C-5' of nucleocidin from [ 2 H5]glycerol 2c and also from (R)-[ 2 H2]-glycerol in our previous experiment,9 and that single deuteriums are retained from each of (1R,2R)-[ 2 H1]-2a and (1S,2R)-[ 2 H1]-2b glycerols.…”

“…A feeding experiment with [ 2 H5]-glycerol 2c showed again a population of nucleocidin molecules with an 0.22 ppm upfield shift in the resultant 19 F-NMR signal, as observed previously. 9 Since this is twice the magnitude of the induced shift relative to the feeding experiments with glycerols 2a and 2b, we are forced to conclude that…”

“…We recently reported isotopically labelled glycerol incorporations into nucleocidin 1 after incubations with whole cell fermentations of S. calvus. 9 In those experiments it was demonstrated that C-2 of glycerol became C-4' of nucleocidin, after a feeding experiment with [2-13 C]-glycerol. This was obvious from the 45 large 2 JCF coupling of 232 Hz in the 19 F-NMR spectrum of the isolated nucleocidin.…”

Hot off the press

“…Feeding studies with deuterium and carbon-13 labelled glycerols have provided the first biosynthetic data of the antibiotic nucleocidin 26 in Streptomyces calvus. 24 The presence of only a single deuterium atom from [ 2 H 5 ]-and (R)-[ 2 H 5 ]glycerol at the C-5' of nucleocidin suggests that oxidation of this position occurs after ribose ring assembly and before or during introduction of the fluorine atom.…”