Adenylate kinases in man: evidence for a third locus

The tissue distribution of the adenylate kinase isozymes in man has been examined using various substrates. The isozymes attributable to the AK1 and AK2 loci were identified, and an additional set of isozymes probably attributable to a third locus was also found. This locus has been provisionally designated AK3. The AK3 isozymes show activity with either GTP + AMP or ITP + AMP but do not show activity with ATP + AMP. They also differ from the AK1 and AK2 isozymes in electrophoretic mobility and from the AK1 isozymes in being resistant to silver inhibition. They are similar in molecular size to the AK1 isozymes whereas the AK2 isozymes are apparently larger. The AK3 isozymes evidently correspond to the enzyme nucleosidetriphosphate-adenylate kinase (2.7.4.10). Somatic cell hybrid studies indicate that the AK3 locus is not syntenic with that of AK2 (chromosome 1). The AK3 locus is however, probably syntenic with the AK1 locus, on chromosome 9. Genetically determined variation of AK3 has not been seen in a survey of about 80 individuals.