The deletion or mutation of specific enzymes involved in amino acid metabolism can significantly affect the biosynthesis of neurotransmitters such as dopamine, serotonin, and GABA in the human brain. These neurotransmitters are synthesized from amino acid precursors, and the enzymes involved in their biosynthesis play crucial roles in their production. Any disruption in the function of these enzymes can lead to imbalances in neurotransmitter levels, which can, in turn, affect brain function and contribute to various neurological and psychiatric disorders.1. Dopamine: Dopamine is synthesized from the amino acid tyrosine. The key enzymes involved in this process are tyrosine hydroxylase TH and aromatic L-amino acid decarboxylase AADC . Tyrosine hydroxylase converts tyrosine to L-DOPA, and AADC then converts L-DOPA to dopamine. Deletion or mutation of either of these enzymes can lead to reduced dopamine synthesis, which can contribute to conditions such as Parkinson's disease, attention deficit hyperactivity disorder ADHD , and schizophrenia.2. Serotonin: Serotonin is synthesized from the amino acid tryptophan. The key enzymes involved in this process are tryptophan hydroxylase TPH and aromatic L-amino acid decarboxylase AADC . Tryptophan hydroxylase converts tryptophan to 5-hydroxytryptophan 5-HTP , and AADC then converts 5-HTP to serotonin 5-HT . Deletion or mutation of either of these enzymes can lead to reduced serotonin synthesis, which can contribute to conditions such as depression, anxiety, and obsessive-compulsive disorder OCD .3. GABA: GABA gamma-aminobutyric acid is synthesized from the amino acid glutamate. The key enzyme involved in this process is glutamic acid decarboxylase GAD , which converts glutamate to GABA. Deletion or mutation of this enzyme can lead to reduced GABA synthesis, which can contribute to conditions such as epilepsy, anxiety, and Huntington's disease.In summary, the deletion or mutation of specific enzymes involved in amino acid metabolism can have significant consequences for the biosynthesis of neurotransmitters in the human brain. These disruptions can lead to imbalances in neurotransmitter levels, which can contribute to various neurological and psychiatric disorders. Understanding the role of these enzymes in neurotransmitter biosynthesis can help in the development of targeted therapies for these conditions.