Stabilization of human prostatic acid phosphatase by cross-linking with diamines

The acid phosphatase [EC 3.1.3.2] from human prostate gland is very unstable glycoprotein. To stabilize the enzyme cross-linking reaction with diamines was adopted. The carboxyl groups of the enzyme were activated with 1-ethyl-(3-dimethylaminopropyl)-carbodiimide and then treated with diamines of H2N-(CH2)n-NH2 type. The modified enzyme with 1,12-dodecamethylenediamine preserved about 80% of its original activity and showed enhanced thermostability. Gel filtration and SDS-polyacrylamide gel electrophoresis showed the formation of cross-linked products with original molecular weight 100 KD and higher enzymatically active species.