Glycans, enzyme reactions

Insulin acts by binding to insulin receptors on cell membrane. The insulin receptor complex is internalized. By phosphorylation and dephosphorylation reactions there is stimulation or inhibition of enzymes involved in metabolic actions of insulin. Second messengers like phosphatidyl inositol glycan and DAG also mediate the action of insulin on metabolic enzymes. 

For the study of polyprenyl glycosyl phosphates as intermediates in the synthesis of complex glycans, several techniques have been developed, and these have been described elsewhere in detail.18 20 Two important features should be emphasized. First, the very small amounts of polyprenyl phosphates that are present in most tissues for this reason, the use of radioactive techniques for the detection of products is obligatory. Second, on account of the hydrophobic nature of these compounds, and as the enzymes involved in the reactions are membrane-bound, the use of detergents and organic solvents becomes necessary. 

This glycan was extracted by a trichloroacetic acid method and purified to homogeneity by alcohol precipitation and bio-gel filtration methods. The complete molecular structure of the glycan has been deduced from data of methylation analysis in combination with enzymic and chemical degradation reactions (25,... 

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