Isoelectric focusing of serum alkaline phosphatase isoenzymes.

We present a new method for the separation of alkaline phosphatase isoenzymes based on isoelectric focusing of serum proteins. Sera of healthy subjects studied by this method present seven groups of bands within a pH range of 3-9. To date, the organ source of six out of seven groups has been identified directly or indirectly. Serum of patients with histologically proven malignant neoplasms showed an additional group in the pH range 3.6-4.2. This fraction seems to be heterogeneous with respect to the pattern and stability to heat, and to L-phenylalanine and L-homoarginine inhibition. It was present in all but two of the proven malignant tumour patients but also in 26 out of 70 with benign disorders.