Glucosyl phosphate labeled with

As evidence for reaction (1), 1 mole of D-glucosyl phosphate was formed per mole of UDP-glucose and D-galactosyl phosphate consumed when the last two compounds were incubated with an extract of Saccharomyces fragilis.13,w Experiments188 with C14-labeled D-glucosyl phosphate also favor the mechanism represented by reactions (1) and (2). 

A later study in a hard-water meso-trophic lake also investigated the separate fate of i C- and P-labelled glucose 6-phosphate into bacterial-sized particles and phytoplankton (Hernandez et al., 1996). Aquatic bacteria and phytoplankton assimilated the phosphoryl moiety 100 times faster than they assimilated the glucosyl moiety. Bacterial uptake conformed to Michaelis-Menten kinetics with an apparent K, of 86 nM and a of 1.4 nM/min. Phytoplankton took up phosphoryl with an apparent K of 380 nM and a V of 7.6 nM/min. These investigators determined the concentration of naturally occurring phosphate monoesters to be between 25 and 40 nM. Comparison of the rate of phosphoryl uptake from glucose 6-phosphate with the phosphate uptake rate indicated that phytoplankton could satisfy a significant portion (42-99%) of their phosphorus demand by hydrolysis of phosphate monoesters. A similar comparison indicated that bacterial assimilation of phosphorus from... 

The priming capacity of the polysaccharide fraction was confirmed by labeling experiments. Incubation of the purifie cytosolic phosphory-lase isozyme with the polysaccahride fraction and u-glucose 1-phosphate resulted in an effective incorporation of labeled glucosyl residues into the high molecular weight polysaccharide (data not shown). 

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