The monoamine oxidase is an enzyme that catalyzes the oxidative deamination of many amines like serotonin, norepinephrine, epinephrine, and dopamine. There are 2 isoforms of this protein: A and B. The first one is found in cells located in the periphery and breakdown serotonin, norepinephrine, epinephrine, dopamine, and tyramine. The second one, the B isoform, breakdowns phenylethylamine, norepinephrine, epinephrine, dopamine, and tyramine. This isoform is found in the extracellular tissues and mostly in the brain. An amine oxidase is an enzyme that catalyzes the oxidative cleavage of alkylamines into aldehydes and ammonia. Amine oxidases are divided into two subfamilies based on the cofactor they contain. Amine oxidases catalyze oxidative deamination reactions, producing ammonia and an aldehyde. These enzymes are critical to both homeostatic and xenobiotic metabolic pathways and are involved in the biotransformation of aminergic neurotransmitters (such as catecholamines, histamine, and serotonin) as well as toxins and carcinogens in foods and the environment. The monoamine oxidases (MAOs) are well studied and have been targets for drug therapy for more than 60 years. MAOs are flavin-containing mitochondrial enzymes distributed throughout the body. In humans, two isoenzymes of MAO have been identified, encoded by two genes located on the X chromosome: MAO-A and MAO-B. Each isoenzyme can be distinguished by certain substrate specificities and anatomic distribution (Table 4.9), although MAO-A has the distinction of being the sole catecholamine metabolic enzyme in sympathetic neurons. In neural and other selective tissues, MAOs catalyze the first step in the degradation of catecholamines into their aldehyde intermediaries, which is further processed by catechol-O-methyltransferase. The ubiquity of biogenic amines and their central role in neural and cardiovascular function make MAOs highly relevant to clinical anesthesia. The interactions between MAO inhibitors and drugs commonly used in anesthesia have been well described. Although genetic polymorphisms in MAO genes exist and are of great interest in the fields of neurology and psychiatry, to date none have been identified that specifically concern the handling of anesthetic agents.

Amine Oxidase Serotonin References