Glucosylglycerol and glucosylglycerate as enzyme stabilizers.

Compatible solutes constitute a diverse class of low-molecular-mass organic molecules that are accumulated in high intracellular concentrations in response to the external stress of hyperosmolality or high temperature. Many of these compounds like alpha, alpha-trehalose are well known for their stabilizing effect on protein structure and could lead to development of more stable protein formulations. Negatively charged solutes like mannosylglycerate (R-2-O-alpha-D-mannopyranosyl-glycerate) are widespread among (hyper)thermophilic microorganisms and are thought to be exceptionally potent stabilizers of proteins under high-temperature denaturation conditions. To further inquire into the role of compound charge for protective function, we have compared two naturally occurring and structurally related solutes, glucosylglycerol (2-O-alpha-D-glucopyranosyl-sn-glycerol) and glucosylglycerate (R-2-O-alpha-D-glucopyranosyl-glycerate), as stabilizers of different enzymes undergoing inactivation through elevated temperature or freeze drying, and benchmarked their effects against that of alpha,alpha-trehalose. Glucosylglycerate in concentrations of >/=0.1 M was the most effective in preventing thermally induced loss of enzyme activity of lactate dehydrogenase, mannitol dehydrogenase, starch phosphorylase, and xylose reductase. alpha,alpha-Trehalose could usually be replaced by glucosylglycerol without compromising enzyme stability. Glucosylglycerol and glucosylglycerate afforded substantial (eightfold) protection to mannitol dehydrogenase during freeze drying.