Paulomycin A2

Paulomycins (PAUs) refer to a group of glycosylated antibiotics with attractive antibacterial activities against Gram-positive bacteria. They contain a special ring A moiety that is prone to dehydrate between C-4 and C-5 to a quinone-type form at acidic condition, which will reduce the antibacterial activities of PAUs significantly. Elucidation of the biosynthetic mechanism of the ring A moiety may facilitate its structure modifications by combinatorial biosynthesis to generate PAU analogues with enhanced bioactivity or stability. Previous studies showed that the ring A moiety is derived from chorismate, which is converted to 3-hydroxyanthranilic acid (3-HAA) by a 2-amino-2-deoxyisochorismate (ADIC) synthase, a 2,3-dihydro-3-hydroxyanthranilic acid (DHHA) synthase, and a DHHA dehydrogenase. Unfortunately, little is known about the conversion process from 3-HAA to the highly decorated ring A moiety of PAUs. In this work, we characterized Pau17 as an unprecedented 3-HAA 6-hydroxylase responsible for the conversion of 3-HAA to 3,6-DHAA by in vivo and in vitro studies, pushing one step forward toward elucidating the biosynthetic mechanism of the ring A moiety of PAUs.

Paulomycin A2 (C34H46N2O17S), paulomycin C (C32H42N2O17S), paulomycin D (C31H40N2O17S), paulomycin E (C29H36N2O16S) and paulomycin F (C29H38N2O16S) have been isolated from fermentations of Streptomyces paulus strain 273. The structure of these compounds was determined using NMR and mass spectroscopic techniques. The new paulomycins, like paulomycins A and B (J. Antibiotics 35: 285-294, 1982) are highly active mainly against Gram-positive organisms.