Preparation of glycosyl phosphates: β-D-glucopyranosyl phosphate

Development and Application of a High-Throughput Functional Metagenomic Screen for Glycoside Phosphorylases

Glycoside phosphorylases (GPs) catalyze the reversible phosphorolysis of glycosidic bonds, releasing sugar 1-phosphates. To identify a greater range of these under-appreciated enzymes, we have developed a high-throughput functional screening method based on molybdenum blue formation. In a proof-of-principle screen focused on cellulose-degrading GPs we interrogated ∼23,000 large insert (fosmid) clones sourced from microbial communities inhabiting two separate environments and identified seven novel GPs from carbohydrate active enzyme family GH94 and one from GH149. Characterization identified cellobiose phosphorylases, cellodextrin phosphorylases, laminaribiose phosphorylases, and a β-1,3-glucan phosphorylase. To demonstrate the versatility of the screening method, varying substrate combinations were used to identify GP activity from families GH13, GH65, GH112, and GH130 in addition to GH94 and GH149. These pilot screen and substrate versatility results provide a screening paradigm platform for recovering diverse GPs from uncultivated microbial communities acting on different substrates with considerable potential to unravel previously unknown degradative pathways within microbiomes.

First stereoselective synthesis of 2-deoxy-alpha-D-ribosyl-1-phosphate: novel application of crystallization-induced asymmetric transformation

A first stereoselective synthesis of bis(cyclohexylamine) 2-deoxy-alpha-D-ribosyl-1-phosphate has been achieved. The synthesis features a key crystallization-induced asymmetric transformation (AT) to generate a desired alpha-anomer in 99% yield at a 98.8:1.2 ratio of alpha/beta.

Partial purification and some properties of beta-phosphoglucomutase from Lactobacillus brevis

A phosphoglucomutase (beta-phosphoglucomutase) specific for beta-glucose 1-phosphate, which catalyzes the beta-glucose 1-phosphate:glucose 6-phosphate interconversion, was 560-fold purified from Lactobacillus brevis strain L6. The isoelectric point of beta-phosphoglucomutase was 3.8 and it had an apparent molecular weight of 29,000 estimated by gel chromatography. The enzyme required a divalent cation (Mn2+ greater than Mg2+ greater than Ni2+ greater than Co2+) and beta-glucose 1,6-bisphosphate for activity. The equilibrium constant Ke for the reaction beta-D-glucose 1-phosphate in equilibrium D-glucose 6-phosphate at 30 degrees C and pH 6.7 is 18.5. beta-phosphoglucomutase had a pH optimum between 6.3 and 6.8 and appeared to be quite specific: alpha-glucose 1-phosphate, alpha- or beta-galactose 1-phosphate and alpha- or beta-N-acetylglucosamine 1-phosphate did not substitute for beta-glucose 1-phosphate. Double reciprocal plots of the data from initial velocity studies at five beta-glucose 1-phosphate concentrations (10 to 100 microM) and four beta-glucose 1,6-bisphosphate concentrations (0.125 to 1.0 microM) showed that the apparent Michaelis constants for beta-glucose 1-phosphate and beta-glucose 1,6-bisphosphate were related to the concentrations of beta-glucose 1,6-bisphosphate and beta-glucose 1-phosphate, respectively, in such a way as to suggest a ping-pong mechanism. The same conclusion was obtained when substrate-velocity relationships were investigated at fixed ratio of both substrates: the Lineweaver-Burk plots showed linear lines and no parabolic ones. The "true" Km for beta-glucose 1-phosphate and beta-glucose 1,6-bisphosphate were found to be about 12 and 0.8 microM, respectively.

Synthesis of beta-L-fucopyranosyl phosphate and L-fucofuranosyl phosphates by the MacDonald procedure

Fusion of beta-L-fucopyranose tetraacetate with phosphoric acid for 1 min at 50 degrees gives a 9:1 anomeric mixture of the alpha- and beta-pyranosyl phosphates. Longer fusion times give the alpha-anomer exclusively. The L-fucofuranose tetraacetates were synthesized for the first time by acetolysis of methyl-2,3,5-tri-O-acetyl-beta-L-fucofuranoside. Fusion of the furanose tetraacetates with phosphoric acid gave a mixture of the fucofuranosyl phosphates in which the beta-anomer predominated (beta/alpha= 2.4). Anomeric pairs in the fucofuranose series appear to be distinguishable by the chemical shift of the C-6 methyl protons, as already shown by Sinclair and Sleeter in the pyranose series.