CDK5 and Alzheimer disease: The multifactorial pathogenesis of AD involves the dysregulation of key enzymatic targets, including AChE (impairment of neurotransmitter acetylcholine and Aβ aggregation), CDK5/p25 (Tau hyperphosphorylation), GSK-3β (neurofibrillary tangle formation), and MAO-B (H2O2-mediated oxidative stress and Aβ/Tau pathology crosstalk) [46,47,48,49].