Do co-translated product(s) of lactase-phlorizin hydrolase accumulate in the rat intestine?

The 225 kDa precursor of intestinal lactase-phlorizin hydrolase (LPH) consists of four tandemly-organized homologous domains flanked by a signal peptide at the N-end and by a transmembrane anchor at the C-end of the polypeptide chain. While the mature LPH of 130 kDa has already been shown to originate from the C-half of the precursor, no protein deriving from the N-half has been identified so far. Using monospecific antibodies raised against the mature LPH or against a recombinant protein containing the sequence of the N-end of the LPH precursor, we have searched for co-translated protein(s) of LPH in enterocytes and in the intestinal lumen of suckling rats. Since no additional protein to LPH was revealed by these antibodies, it is suggested that the polypeptide chain corresponding to the N-half of the LPH precursor undergoes rapid turnover.