STABLE-ISOTOPE STUDIES OF GLUTAMATE CATABOLISM IN FUSOBACTERIUM-NUCLEATUM

Catabolism of glutamate was investigated in Fusobacterium nucleatum, a n anaerobic micro-organism that is strongly implicated in periodontal disease. The distribution of labels in acetate and butyrate derived fr om [C-13]glutamates was determined by NMR spectroscopy and MS. The lab el from L-[5-C-13]glutamate was not incorporated, whereas C-1 of aceta te and butyrate were efficiently labelled by L-[1-C-13]glutamate; thes e results indicated that the hydroxyglutarate pathway predominated. In butyrate, enrichment at C-3 was smaller than C-1; that this was not d ue to participation of the methylaspartate pathway was demonstrated by the incorporation of label from L-[4-C-13]glutamate into only C-2 of acetate and C-4 (major)/C-2 (minor) of butyrate. The presence of label at a second site in butyrate was attributed to the synthesis of butyr ate from acetate and verified by the incorporation of label from [1,2- C-13(2)]- and [H-2(3)]-acetate.