Many maize inbreds lack an endosperm cytosolic phosphoglucomutase.

Starch gel electrophoresis of extracts from developing maize (Zea mays L.) endosperms 22 days postpollination reveals only a single zone of phosphoglucomutase activity in the majority of the inbreds tested. The other inbreds had the expected two zones of activity. The activity that is present in all inbreds is the amyloplast isozyme while the absent form is a cytosolic enzyme. The lack of the cytosolic isozyme has no discernible phenotypic consequences.