Apparent 'glucokinase' activity in non-hepatic tissues due to N-acetyl-D-glucosamine kinase

1. Electrophoretic examination of tissue extracts from rat intestinal mucosa, kidney, lung, spleen, mammary gland, adipose tissue, heart muscle and placenta in agarose gels did not reveal the presence of any glucokinase (ATP:D-glucose 6-phosphotransferase, EC 2.7.1.2) activity corresponding to that present in rat liver. 2. All these tissues do contain an enzyme that possesses very high-Km glucose-phosphorylating activity but which has a slightly lower electrophoretic mobility than glucokinase and can be separated from it by various means. 3. This phosphotransferase activity is due to N-acetyl-D-glucosamine kinase (ATP:2-acetamido-2-deoxy-D-glucose 6-phosphotransferase, EC 2.7.1.59), which has been partialyy purified from intestinal mucosa tissue and shown to have similar kinetic properties to the same enzyme previously purified more extensively from liver and kidney. 4. It is suggested that many of the effects reported in the literature of 'glucokinase' activity in non-hepatic tissues are probably due to N-acetyl-D-glucosamine kinase.