Neurotransmitters are molecules needed to send messages either from nerve cells to muscles and glands, or between nerve cells to enable the message to be sent through the nervous system. Almost all neurotransmitters are derived from amino acids, which are the building blocks of protein. Some of them, such as glutamate, glycine and aspartate are amino acids which act as neurotransmitters.
Most neurotransmitters are produced using enzymes which are found within the nerve cell that is going to send the message. Once the nerve cell has used an enzyme to produce a neurotransmitter, the neurotransmitter will then be transported to a receptor on the receiving cell. The receptors are specific to the transmitter and they regulate the chemical message that has been sent. Once this has been completed, the transmitter is effectively collected by another transporter and taken back to the nerve cell to be recycled or broken down in the cell. Disorders of neurotransmitter metabolism are caused by problems in the transport of neurotransmitters or in the chemical reactions which allow them to carry out their role or be broken down/recycled. This rare group of disorders can cause neurological problems at any age.