Involved in maintaining the homeostasis of cellular nucleotides by catalyzing the interconversion of nucleoside phosphates (By similarity). Efficiently phosphorylates AMP and dAMP using ATP as phosphate donor, but phosphorylates only AMP when using GTP as phosphate donor (By similarity). Also displays broad nucleoside diphosphate kinase activity (By similarity). Plays a role in controlling cellular ATP levels by regulating phosphorylation and activation of the energy sensor protein kinase AMPK (By similarity). Plays a protective role in the cellular response to oxidative stress (By similarity). a ribonucleoside 5'-triphosphate + AMP = a ribonucleoside 5'-diphosphate + ADP a 2'-deoxyribonucleoside 5'-diphosphate + ATP = a 2'-deoxyribonucleoside 5'-triphosphate + ADP a ribonucleoside 5'-diphosphate + ATP = a ribonucleoside 5'-triphosphate + ADP Monomer (By similarity). Interacts with SLC25A5/ANT2 (By similarity). Expressed in kidney, liver, stomach, brain, spinal cord, heart, ovary, oviduct, colon, jejunum, ileum and testis (at protein level) (PubMed:19492028, PubMed:19130895). In the brain, expressed in the pyramidal cells of the cerebrum and glial cells in the cerebellum (at protein level) (PubMed:19492028). In the heart, expressed by myocytes (at protein level) (PubMed:19492028). In the kidney, expressed in the proximal to distal tubule in the cortex and the outer and inner zones of the medulla (at protein level) (PubMed:19492028). In the stomach, expressed in stratified squamous epithelia in the forestomach and in the gastric pit and mucus producing cells of the glandular stomach (at protein level) (PubMed:19492028). Expressed in epithelial cells of the jejunum, ileum, and colon (at protein level) (PubMed:19492028). In the testis, expressed by spermatocytes (at protein level) (PubMed:19492028). In the ovaries, expressed by oocytes, follicular epithelial cells, and corpus luteum cells (at protein level) (PubMed:19492028). In the oviduct, expressed in the epithelia of the isthmus and the ciliated cells of the ampulla (at protein level) (PubMed:19492028). Expressed in the pyramidal cells in the hippocampus (PubMed:9813319). Expressed in the central nervous system in a region-specific manner from the middle stage of embryogenesis to the adulthood in the rodent. Consists of three domains, a large central CORE domain and two small peripheral domains, NMPbind and LID, which undergo movements during catalysis. The LID domain closes over the site of phosphoryl transfer upon GTP/ATP binding. Assembling and dissambling the active center during each catalytic cycle provides an effective means to prevent GTP/ATP hydrolysis. Belongs to the adenylate kinase family. AK3 subfamily.