Genetically determined polymorphism of a form of hexokinase, HK III, found in human leucocytes.

1. A form of hexokinase which appears to correspond to HK III, seen in liver, spleen and lung, has been identified in human polymorphonuclear leucocytes. HK III activity has not been demonstrated in lymphocytes, permanent lymphoblastoid cell lines or in cultured fibroblasts. 2. In fresh leucocyte preparations HK III usually appeared as a single band, but in extracts of post-mortem tissues multibanded patterns were seen. Leucocyte preparations also give multi-banded patterns after storage for more than a few hours. 3. In certain individuals the HK III showed a two-banded pattern even in fresh preparations. Repeat samples and family studies suggested that this pattern was genetically determined and represented a heterozygote for a common allele HK1III and a less common variant HK2III. Out of a total of 330 English people successfully tested 10 probable heterozygotes were found. 4. It is suggested that HK III may be a monomeric enzyme whose genetic determination is independent of that of the other main forms of hexokinase.