CARBOHYDRATE FLUXES INTO ALGINATE BIOSYNTHESIS IN AZOTOBACTER-VINELANDII NCIB-8789 - NMR INVESTIGATIONS OF THE TRIOSE POOLS

The metabolite flux of carbohydrates through primary catabolism and in to hexose resynthesis has been investigated for alginic acid biosynthe sis in Azotobacter vinelandii. To do these studies, we fed the microor ganism a variety of C-13-labeled glucose precursors, including [U-C-13 (6)]glucose. The incorporations of the precursors were determined by 1 D C-13-NMR, 2D C-13-DQF-COSY, and inverse triple-quantum correlation e xperiments. The results clearly show that the entire catabolism of hex ose is through the Entner-Doudoroff (E-D) pathway and that the triose pools are in equilibrium. Reentry into gluconeogenesis prior to algina te synthesis occurs totally from the glyceraldehyde 3-phosphate genera ted by the E-D pathway. The obligatory intermediacy of triose intermed iates in alginate biosynthesis was proved. The experiments and results presented in this paper constitute a new method for distinguishing th e E-D pathway from glycolysis in bacteria.