Nature of the multiple forms of alanine aminopeptidase

Alanine aminopeptidase (particle-bound aminopeptidase, EC 3.4.11.2) isolated in a highly purified state from human liver, kidney, and pancreas were investigated with regard to their different electrophoretic mobilities. While the molecular weights are identical, different isoelectric points were found. The results of carbohydrate analysis point to N-acetylneuraminic acid as the main factor that causes the differences in electrophoretic behaviour of the alanine aminopeptidases investigated.