Tripeptidyl-peptidase I is apparently the CLN2 protein absent in classical late-infantile neuronal ceroid lipofuscinosis.

We report that fragments of amino acid sequence recently described for tripeptidyl-peptidase I (TPP I) show that it is the rat homologue of the human CLN2 gene product that is deficient in classical late-infantile neuronal ceroid lipofuscinosis. This is unexpected, since the CLN2 protein has been thought to be a carboxyl-dependent endopeptidase, but TPP I is an exopeptidase possibly of serine-type.