In addition, the formation of reactive oxygen and nitrogen species due to the deficiency and abnormal function of cytosolic and membrane enzymes, significantly contributes to metabolic stress in AD.(68) Among the enzymes affected in this process are NAD(P)H oxidase (NOx), cytochrome p450, monoamine oxidase enzyme (MAO), xanthine oxidase (XO), nitric oxide synthase (NOS), and myeloperoxidase (MPO).(69). Here, XDH is linked to Alzheimer disease.