Is dextrose an optical isomer of glucose?
If a microorganism metabolises glucose, would it also be capable of metabolising dextrose? Do both 'fit' into the same enzyme that binds to glucose?
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There are two enantiomeric forms of glucose, D- and L, with D-glucose being the naturally occurring form. Dextrose is just another common name for D-glucose, so if a microorganism can metabolise D-glucose then it can by definition metabolise dextrose as they are just two words for the same thing.
As for the question of whether the enzyme would recognise both optical isomers (enantiomers), this would probably not be the case. Enzymes are 'chiral', as are the two enantiomers of glucose. The active sites of enzymes/proteins are often specific for a given isomer, hence why many drugs are only biologically active in one enantiomeric form, with the other enantiomer being either inactive, less active, or in certain cases toxic.
In particular, the first step in glucose metabolism is phosphorylation of the C-6 hydroxyl group by the enzyme hexokinase. However, hexokinase is incapable of phosphorylating L-glucose.