HTHSCI 1I06 Lecture Notes - Lecture 3: Glycogen Phosphorylase, Signal Transduction, Cell Signaling
20 Mar 2019
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Document Summary
Histamine is a molecule, composed of imidazole and a side chain, 4-ethanamine, that has many effects such as; contraction; relaxation; neurotransmission. Sutherland and his colleagues were investigating how the animal hormone epinephrine (adrenaline) stimulates the breakdown of the storage polysaccharide, glycogen, within liver cells and skeletal muscle cells (to produce glucose 6-phosphate). His research team discovered that epinephrine stimulates glycogen breakdown by somehow activating a cytosolic enzyme, glycogen phosphorylase. However, when epinephrine was added to a test-tube mixture containing the enzyme and its substrate, glycogen, no breakdown occurred. Glycogen phosphorylase could be activated by epinephrine only when the hormone was added to intact cells in a solution. Epinephrine does not interact directly with the enzyme responsible for glycogen breakdown; an intermediate step or series of steps must be occurring inside the cell. The plasma membrane itself is necessary for the transmission of the signal to take place.
