Existence of a human urinary trypsin inhibitor (urinastatin)-like substance in the rat brain.

A human urinary trypsin inhibitor, urinastatin (UT)-like immunoreactive substance with trypsin inhibitory activity, was demonstrated in certain brain regions in rats, especially the cerebral cortex, hippocampus and hypothalamus. Although this UT-like substance in the rat brain displayed an N-terminal amino acid sequence similar to that of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), it did not show any GAPDH activity. These results indicate that the UT-like substance in the rat brain is a protein different from GAPDH and indicates a localized distribution within certain brain regions partly related to learning and memory.