Glutamate is by far the most frequently found amino acid in spider venoms. In insects, the excitatory neurotransmitter acts at the neuromuscular junctions targeting glutamate receptors (GluRs). The activated GluRs channels can then for example be inhibited by aclypolyamines which cause a reversible paralysis of the spider’s prey. This is why some spiders (Araneidae and Nephilidae) have glutamate in their venom as well as acylpolyamines. Other venoms (Agelenidae) do not contain glutamate but stimulate the release of the neurotransmitter from pre-synaptic terminals by peptide toxins.
Other amino acids are expected to occure in spider venom but have rarely been reported.
For a more detailed discussion of amino acids in spider venom we recommend having a look at the outstanding article “Venom composition and strategies in spiders: Is everything possible?” (Kuhn-Nentwig, 2011).