Lecture 13, part 1: Synthesis and Storage of Excitatory Amino Acids Flashcards
excitatory amino acids
glutamate and aspartate
inhibitory amino acids
GABBA and glycine
how do glutamate and aspartate differ in structure
glutamate has an extra CH2
glutamate and aspartate are the most abundant free amino acids in which organ?
brain
how is glutamate synthesised?
glycolysis and from glutamine
what are the order of products made in glycolysis?
pyruvate- acetyl coa- alpha ketoglutarate- glutamate
what is the role of glutaminase?
catalyses the conversion of glutamine into glutamate
how is glutamate mostly synthesised?
from glutamine
how is glutamate synthesis controlled?
glutamate negatively feedbacks onto glutaminase
explain the glutamine cycle within astrocytes
glutamine synthetase converts glutamate into glutamine
in order for glutamate synthesis, what enters the presynaptic terminal from glial cells?
glutamine
what happens to the excess glutamate?
taken up by glial cells and presynaptic terminals
why is it important that glutamate is re uptaken?
so that it can be converted into glutamine
reversal of transaminase reaction and glutamate dehydrogenase produces what?
alpha ketoglutarate
what are the glutamate transporters?
VGLUT1, 2 and 3
describe the specificity of glutamate transporters
specific for L-glutamate
what transporters allow for glutamate entry into vesicles?
H+ antiporters
how is ATP important in glutamate transport?
energy required to create proton gradients that allow for glutamate entry into the vesicle
VGLUT1 is mostly expressed where?
afferent neurons
where is VGLUT2 mostly expressed?
CNS
glutamate transporters direction of activity
can remove or release glutamate
how do vesicles and transporters differ in their specificity?
transporters have a low specificity (except they do not transport D-Glu)
what are excitatory amino acid transporters termed as?
EEAT (1-5)
the affinity of excitatory transporters:
10-40 micromolar
features of glutamate transporters
525-573 amino acids
6-10 transmembrane domains
55% homology
alterations seen in pathology
where is EAAT2 found?
astrocytes
where is EAAT3 found
neurons
where is EAAT5 found
retina
EAAT1 location
cortical, hippocampal and cerebellular neurons and astroglia
EAAT4 location
cerebellar purkinje cells
role of VGLULT
packages glutamate into vesicles
which glutamate transporters are found in glial cells?
EAAT2 and EAAT1
which glutamate transporters are post synaptic ?
EAAT3 and EAAT4
