Characterization of rat hepatoma glucosamine 6-phosphate synthase and its relation to liver and fetal forms

Glucosamine 6-phosphate synthase (EC 5.3.1.19) purified from various rat tissues by a procedure involving chromatography on diethylaminoethyl Sephadex and hydroxylapatite were characterized by means of isoelectric focusing. The non-hepatic isozyme, previously reported to be present in Yoshida sarcoma, has a pI of 4.1 and is distinguished from the hepatic isozyme, with a pI of 5.0. The pI 4.1 form is the major one in all of the fast-growing, transplantable hepatomas studied. Although not detectable in 19-day fetal liver or normal adult liver, the pI 4.1 form has been observed in the whole 12-day fetus and adult brain as almost the sole form of glucosamine 6-phosphate synthase.