Acts as a serine/threonine-protein kinase (PubMed:16672980, PubMed:18799731, PubMed:16672981, PubMed:16818890, PubMed:16938835, PubMed:18230723, PubMed:18443288, PubMed:18957282, PubMed:20194754, PubMed:22645651, PubMed:24901221, PubMed:25474007, PubMed:32484300). Exhibits a substrate preference for proline at position P+1 and a general preference at several residues for basic residues such as arginine (By similarity). Also exhibits moderate preferences for a phosphotyrosine at position P-3 and a tryptophan at P-5 (By similarity). Protects against mitochondrial dysfunction during cellular stress by phosphorylating mitochondrial proteins such as park and likely Drp1, to coordinate mitochondrial quality control mechanisms that remove and replace dysfunctional mitochondrial components (PubMed:16672980, PubMed:18799731, PubMed:16672981, PubMed:16818890, PubMed:16938835, PubMed:18230723, PubMed:18443288, PubMed:18957282, PubMed:20194754, PubMed:22645651, PubMed:24901221, PubMed:25474007, PubMed:32484300). Depending on the severity of mitochondrial damage and/or dysfunction, activity ranges from preventing apoptosis and stimulating mitochondrial biogenesis to regulating mitochondrial dynamics and eliminating severely damaged mitochondria via mitophagy (PubMed:16672980, PubMed:16672981, PubMed:16818890, PubMed:16938835, PubMed:18230723, PubMed:18443288, PubMed:18799731, PubMed:18957282, PubMed:20194754, PubMed:23509287, PubMed:24901221, PubMed:25474007). Appears to be particularly important in maintaining the physiology and function of cells with high energy demands that are undergoing stress or altered metabolic environment, including spermatids, muscle cells and neurons such as the dopaminergic (DA) neurons (PubMed:16672980, PubMed:16672981, PubMed:16818890, PubMed:16938835, PubMed:18443288, PubMed:18799731, PubMed:22396657, PubMed:24901221, PubMed:28435104, PubMed:32138754). Mediates the translocation and activation of park at the outer membrane (OMM) of dysfunctional/depolarized mitochondria (PubMed:24901221, PubMed:20194754, PubMed:18957282, PubMed:18799731, PubMed:25474007, PubMed:27906179). At the OMM of damaged mitochondria, phosphorylates pre-existing polyubiquitin chains, the Pink1-phosphorylated polyubiquitin then recruits park from the cytosol to the OMM where park is fully activated by phosphorylation at 'Ser-94' by Pink1 (PubMed:24901221, PubMed:20194754, PubMed:18957282, PubMed:18799731, PubMed:25474007, PubMed:27906179). When cellular stress results in irreversible mitochondrial damage, functions with park to promote the clearance of dysfunctional and/or depolarized mitochondria by selective autophagy (mitophagy) (PubMed:16672980, PubMed:16672981, PubMed:20194754, PubMed:18957282, PubMed:23509287, PubMed:25474007). The Pink1-park pathway also promotes fission and/or inhibits fusion of damaged mitochondria, by phosphorylating and thus promoting the park-dependent degradation of proteins involved in mitochondrial fusion/fission such as Marf, Opa1 and fzo (PubMed:18443288, PubMed:18799731, PubMed:18230723, PubMed:20194754, PubMed:24901221). This prevents the refusion of unhealthy mitochondria with the mitochondrial network or initiates mitochondrial fragmentation facilitating their later engulfment by autophagosomes (PubMed:18443288, PubMed:18799731, PubMed:18230723, PubMed:20194754, PubMed:24901221). Also likely to promote mitochondrial fission independently of park and Atg7-mediated mitophagy, via the phosphorylation and activation of Drp1 (PubMed:18443288, PubMed:32484300). Regulates motility of damaged mitochondria by phosphorylating Miro which likely promotes its park-dependent degradation by the proteasome; in motor neurons, this inhibits mitochondrial intracellular anterograde transport along the axons which probably increases the chance of the mitochondria being eliminated in the soma (PubMed:22396657). The Pink1-park pathway is also involved in mitochondrial regeneration processes such as promoting mitochondrial biogenesis, activating localized mitochondrial repair, promoting selective turnover of mitochondrial proteins and initiating the mitochondrial import of endogenous proteins (PubMed:16672980, PubMed:23509287, PubMed:30772175). Involved in mitochondrial biogenesis by promoting the park-dependent ubiquitination of transcriptional repressor Paris which leads to its subsequent proteasomal degradation and allows activation of the transcription factor srl (PubMed:32138754). Functions with park to promote localized mitochondrial repair by activating the translation of specific nuclear-encoded mitochondrial RNAs (nc-mtRNAs) on the mitochondrial surface, including several key electron transport chain component nc-mtRNAs (PubMed:23509287). During oogenesis, phosphorylates and inactivates larp on the membrane of defective mitochondria, thus impairing local translation and mtDNA replication and consequently, reducing transmission of deleterious mtDNA mutations to the mature oocyte (PubMed:30772175). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with park (PubMed:19048081). Interacts with rho-7 and HtrA2 (PubMed:19048081). Localizes mostly in mitochondrion, and the smaller proteolytic processed fragment localizes in the cytosol as well (PubMed:19048081). When mitochondria are damaged, defective and/or enriched with deleterious mtDNA mutations, Pink1 import is arrested which induces its accumulation on the outer mitochondrial membrane where it acquires kinase activity (PubMed:18957282, PubMed:30772175). Detected in nebenkerns (PubMed:16672981). High expression in the brain and retinas (PubMed:16938835). High expression in the head and testes (PubMed:16672981). High expression in the thorax compared to the head and abdomen (PubMed:16672980). Expressed throughout development, with high levels of expression in adults and low levels of expression in larvae and pupae (PubMed:16672980, PubMed:16672981). Adult males display higher levels of expression than females (PubMed:16672980). Proteolytically cleaved (PubMed:19048081). In healthy cells, the precursor is continuously imported into mitochondria where it is proteolytically cleaved into its short form by the mitochondrial rhomboid protease rho-7 (PubMed:19048081). The short form is then released into the cytosol where it rapidly undergoes proteasome-dependent degradation (Probable). In unhealthy cells, when cellular stress conditions lead to the loss of mitochondrial membrane potential, mitochondrial import is impaired leading to the precursor accumulating on the outer mitochondrial membrane (OMM) (PubMed:27906179). Autophosphorylated on Ser-346, which activates kinase activity (PubMed:25474007, PubMed:27906179). Loss of mitochondrial membrane potential results in the precursor accumulating on the outer mitochondrial membrane (OMM) where it is activated by autophosphorylation at Ser-346 (PubMed:27906179). Autophosphorylation is sufficient and essential for selective recruitment of park to depolarized mitochondria, likely via Pink1-dependent phosphorylation of polyubiquitin chains (PubMed:25474007, PubMed:27906179). Adults display various phenotypes that appear to be the result of mitochondrial abnormalities and/or mitochondrial dysfunction (PubMed:16672980, PubMed:16672981, PubMed:18799731, PubMed:18443288, PubMed:24901221, PubMed:27906179, PubMed:30772175). In various tissues including the indirect flight muscles (IFM), thoracic muscles, sperm, cardiomyocytes and neurons including the dopaminergic (DA) neurons, mitochondria display abnormalities such as swelling, loss of cristae, fragmentation, aggregation and/or mitochondrial disorganization, and they are dysfunctional resulting in defects such as mitochondrial depolarization, increased reactive oxygen species (ROS) production, reduced ATP, decreased mitochondrial DNA and reduced mitochondrial protein levels (PubMed:16672980, PubMed:16672981, PubMed:18443288, PubMed:18799731, PubMed:24901221, PubMed:27906179, PubMed:23509287). As a result adults are reduced in size, display reduced survival and decreased fertility (PubMed:16672980, PubMed:16672981, PubMed:18799731). They also exhibit age-dependent and progressive degradation of the IFM and DA neurons, especially in the protocerebral posterior lateral 1 (PPL1) cluster, which likely contribute to the observed locomotive defects, down-turned rigid wings and crushed thorax phenotypes (PubMed:16672980, PubMed:18443288, PubMed:24901221, PubMed:27906179). Also affects non-motor behaviors such as reduced learning, intermediate-term memory and irregular circadian rhythms under constant darkness, likely as a result of the neurodegradation (PubMed:28435104). On the surface of mitochondria enriched with a deleterious mutation, negative regulation of larp-mediated protein synthesis is reduced, and as a consequence the transmission of the deleterious mtDNA mutation to the mature oocyte is more random compared to control oocytes which display decreased inheritance of the mutation (PubMed:30772175). RNAi-mediated knockdown increases the net velocity of anterograde mitochondrial transport in motor neurons, whereas retrograde transport is largely unaffected (PubMed:22396657). Double knockout of Pink1 and park display no increase in the severity of their phenotypes compared to single mutants (PubMed:16672980). However, expression of park in Pink1 mutants markedly rescues most of the Pink1 mutant phenotypes, whereas expression of Pink1 in park mutants fails to rescue the defective thorax and abnormal wing position (PubMed:16672980). Double knockout of Pink1 and Drp1 severely disrupts mitochondrial fusion resulting in mitochondrial aggregates and long threads of mitochondrial tubules (PubMed:18443288). Double knockdown with Paris, improves climbing performance defects and rescues decreased mRNA levels of srl, ewg and TFAM, observed in Pink1 mutants (PubMed:32138754). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.