NADK2 and neoplasm: In addition, we show that autophagy promotes proline biosynthesis through mitophagy-mediated regulation of NADK 2 (mitochondrial NAD kinase 2), an enzyme responsible for mitochondrial NADP (H) production, Targeting PRKN (parkin RBR E3 ubiquitin protein ligase) in the matrix to inhibit cellular mitophagy reduced tumor weight.