Partial Purification of Rat and Human Serum Factors Inhibiting the G1‐S Transition in Rat Hepatocytes

Abstract

A low MW compound, which inhibits the G1-S transition in rat hepatocytes, was purified from rat trypsin-treated serum by DEAE-cellulose chromatography and high-performance liquid chromatography on 3 different stationary phases. This procedure led to a 34,500-fold purification, with a 29% yield. Inactivation of the purified material by specific enzymes showed that the inhibitor is a glycopeptide containing a peptide moiety, N-acetylneuraminic acid and galactose residues. Amino acid analyses indicated the possible existence of a pentapeptide structure. The same purification procedure was applied to the corresponding human inhibitor. Inactivation by specific enzymes showed that it is also a glycopeptide.