Pennsylvanicus after cell-wall inhibition biochemical changes in Bifidobacterium bifidum var : VI. Biosynthesis of the galactosyldiglycerides

Abstract

1. 1. A particulate fraction from Bifidobacterium bifidun var. pennsylvanicus synthesized the five major 14C-labelled galactosyldiglycerides from UDP[ 14C]galactose and 1,2-dipalmitin. Diolein and natural diglycerides were rather ineffective substrates. 2. 2. Incorporation and distribution of 14C activity among the different galactosyl-diglycerides were determined after incubation of the particles with the individual galactolipid compounds and UDP[ 14C]galactose. Mono- and digalactosyldiglyceride appeared to be the precursors for di- and trigalactosyldiglyceride, respectively. The same system incorporated UDPgalactopyranose into the acylated galactofuranosyl-diglycerides. 3. 3. The optimal conditions for incorporation were determined. Mn 2+, Mg 2+, Co 2+ and Fe 2+ stimulated the incorporation the most of the nine cations tested, Cu 2+ was a strong inhibitor. Marked differences were observed in the effects of 11 detergents. Myristic and palmitic acid and sodium dodecylsulphate stimulated the incorporation, Triton X-100 and Lubrol W inhibited it. The first galactosylation reaction with dipalmitin as substrate showed a rather broad pH traject (5.0–7.0). The second and third galactosylation reactions with mono- and digalactosyldiglyceride as substrates had a much higher velocity at pH 5.0 than at pH 7.0. 4. 4. The results were compared with the data on glycolipid synthesis in four other bacterial systems and on galactolipid synthesis in brain and chloroplast preparations.