This gene encodes an endo/exonuclease with 5'-3' exonuclease activity. The encoded enzyme catalyzes the hydrolysis of ester linkages at the 5' end of a nucleic acid chain. This enzyme is localized to the mitochondria and may play a role in programmed cell death. Alternatively spliced transcript variants have been described. A pseudogene exists on chromosome 18. [provided by RefSeq, Feb 2009]