It is believed that α-glucosidase, acetylcholinesterase (AChE), and tyrosinase are important metabolic enzymes relating with oxidative stress, and they are shown to be the key targets of T2DM, Alzheimer’s disease (AD), mammalian melanogenesis, and fruit or vegetable enzymatic browning, respectively [30,31,32]. The gene discussed is TYR; the disease is Alzheimer disease.