Presence of proteins and glutamate as major constituents of the venom of the spider Araneus gemma.

The venom from the spider Araneus gemma contains an inhibitor of physiologic glutamate receptors and of glutamate binding sites in brain synaptic membranes. In the present study the chemical composition of the venom was examined in order to determine the presence of constituents that may have physiologically important actions on the prey. The milked venom contains high concentrations of protein (approximately equal to 200 micrograms/microliter) and of glutamate (130-425 mM) and very low concentrations of epinephrine, epinine, dopamine and 3,4-dihydroxyphenylacetic acid. There is also marked heterogeneity in the venom peptides detected by SDS gel electrophoresis. The presence of free glutamate may be very important for the actions of the glutamate receptor inhibitor in the venom.