Abstract Loss of metabolic homeostasis is a hallmark of aging that leads to increased susceptibility to diseases and increased frailty. Although global metabolic reprogramming has been explored in different species, the mechanisms driving this reprogramming are poorly understood. Through a deeper understanding of these processes, the affected metabolic pathways can be directly targeted, paving the way to a delay or even a reversal of aging in model organisms and ultimately in humans. We previously demonstrated that the levels of enzymes in the tyrosine degradation pathway increase with age and that either whole-body or neuronal-specific downregulation of enzymes in the tyrosine degradation pathway significantly extend Drosophila lifespan. Mechanistically, suppression of mitochondrial Electron Transport Chain Complex I (mETC CI) phenocopies aging and drives the upregulation of enzymes in the tyrosine degradation pathway. Although the augmentation of tyrosine catabolism was detrimental to health- and lifespan in our studies, the mechanism driving this age-dependent upregulation is unknown. It is also unknown whether a similar mechanism is responsible for the age-dependent decrease of tyrosine-derived neurotransmitters in mammals including humans. Through our preliminary screen of potential transcription factors/regulators, we identified stonewall (Stwl) as a prospective transcriptional regulator (TR) that is responsible for the upregulation of TAT in response to mETC CI inhibition. Our central hypothesis is that inhibiting Stwl can prevent the augmented tyrosine degradation associated with aging and mitochondrial dysfunction and that this process is conserved in mammals. In this application, we propose to determine the impact of Stwl on the levels of enzymes in the tyrosine degradation pathway, levels of tyrosine-derived neurotransmitters, and Drosophila health- and lifespan (Aim 1); and to test whether the effect of aging/mitochondrial dysfunction on the activity of the tyrosine degradation pathway is conserved in mammals (Aim 2). We expect that the insights we gain will allow us to establish a novel link between aging, mitochondrial dysfunction, tyrosine metabolism, and the production of neurotransmitters.