N-acetylalanine aminopeptidase activity in normal and tumour cells

The catalytic concentration of N-acetylalanine aminopeptidase was determined in erythrocytes, polymorphonuclear leukocytes, lymphocytes, alveolar macrophages, human lung fibroblasts, human lung cancer cells, human umbilical vein endothelial cells, mice Leydig cells, rat tumour cells, and endothelial cells from hog and bovine lung. The catalytic concentration ranged from 0.5 +/- 0.1 nU/cell (erythrocytes) to 35 nU/cell (rat tumour cell line B Sp 73 ASML). Almost all tumour cells showed higher activity levels. No activity was found in human plasma.