Complex sentence: Unlike serotonin, αMS is not metabolized by monoamine oxidase on account of the α-methyl substituent blocking the enzyme access to the amine, and as a result, it has a much longer half-life in comparison.
Split into simpler sentences: Unlike serotonin, αMS is not metabolized by monoamine oxidase on account of the α-methyl substituent blocking the enzyme access to the amine. As a result, it has a much longer half-life in comparison.