MAO-A is an enzyme that plays a crucial role in breaking down neurotransmitters in the brain, such as serotonin, norepinephrine, and dopamine. By regulating the levels of these chemicals, MAO-A helps maintain mood and emotional balance. This enzyme is part of the monoamine oxidase family and is found in various tissues throughout the body, including the brain and liver. Variations in the MAO-A gene can influence an individual's susceptibility to certain mental health conditions, making it an important area of study in psychology and psychiatry.