Jm. Beale et Jl. Foster, CARBOHYDRATE FLUXES INTO ALGINATE BIOSYNTHESIS IN AZOTOBACTER-VINELANDII NCIB-8789 - NMR INVESTIGATIONS OF THE TRIOSE POOLS, Biochemistry, 35(14), 1996, pp. 4492-4501
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.